KS3 Science Study Pack: Waves

Key Knowledge

Waves are one way that energy and information can travel from one place to another. A wave is a disturbance that transfers energy, but it does not transfer matter overall from the source to the receiver. In a sound wave, air particles vibrate backwards and forwards, but the same air particles do not travel all the way from a loudspeaker to your ear. In a water surface wave, the water mainly moves up and down while the wave energy moves across the surface.

A wave usually starts at a source. The source might be a vibrating guitar string, a loudspeaker cone, a lamp, the Sun, a radio transmitter, a moving hand shaking a rope, or a stone dropped into water. The energy travels through the wave to a receiver or detector. Examples of detectors include an ear, an eye, a microphone, a camera, a light sensor, a solar panel, a radio aerial, or a medical scanner.

Waves are used in many everyday situations:

• Sound waves carry energy from instruments and voices to our ears.
• Light waves carry energy from lamps, screens, and the Sun to our eyes.
• Radio waves carry information to radios, televisions, mobile phones, and Wi-Fi devices.
• Ultrasound waves can help doctors make images of the inside of the body.
• Reflected waves can form echoes, mirror images, and sonar measurements.

The most important idea is that waves transfer energy without transferring matter overall.

What Waves Do

When a wave travels, energy moves from the source to another place. The material, if there is one, usually vibrates around a rest position. The particles do not travel along with the wave from start to finish.

For example, imagine a line of students passing a squeeze along a slinky spring. Each coil of the spring moves a short distance and then returns, but the disturbance travels along the spring. This is a model of a mechanical wave. In real sound waves, particles in air, water, or solids vibrate. The sound energy moves onwards.

Waves can also transfer information. A mobile phone signal carries information using electromagnetic waves. A bat sends out sound waves and uses returning echoes to detect insects. A doctor can use ultrasound echoes to build an image of a baby before birth. In each case, the wave carries energy and information to a detector.

Sources, Receivers, and Detectors

Example	Source of wave	Receiver or detector	Energy or information transferred
Guitar music	Vibrating guitar string and body	Ear or microphone	Sound energy and music pattern
Seeing a book	Lamp or Sun, then reflected book surface	Eye	Light energy and information about the book
Solar panel	Sun	Solar panel	Light energy transferred to electrical energy
Sonar on a ship	Sound transmitter	Sound receiver	Information about water depth
Remote control	Infrared LED	TV sensor	Information for changing channel
Radio broadcast	Radio transmitter	Radio aerial	Information for sound and speech

Mechanical and Electromagnetic Waves

Waves can be divided into two main groups: mechanical waves and electromagnetic waves.

Mechanical waves need a material medium. A medium is the material that a wave travels through, such as air, water, glass, metal, or a rope. Sound waves are mechanical waves, so they need particles to vibrate. This is why sound cannot travel through a vacuum. A vacuum is a space with no particles. Space is almost a vacuum, so astronauts cannot hear sound travelling directly through space.

Electromagnetic waves do not need a medium. They can travel through a vacuum. Light from the Sun reaches Earth by travelling through space. Radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays are also electromagnetic waves. They are all transverse waves and they all travel at the same speed in a vacuum.

Feature	Mechanical waves	Electromagnetic waves
Need a medium?	Yes	No
Can travel through a vacuum?	No	Yes
Main KS3 examples	Sound, water waves, waves on a rope, slinky waves	Radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
What vibrates?	Particles of the medium	Electric and magnetic fields, described simply at KS3 as an electromagnetic disturbance
Detectors	Ear, microphone, vibration sensor	Eye, camera, aerial, light sensor, thermal camera, X-ray detector

Transverse and Longitudinal Waves

Waves can also be described by the direction of vibration compared with the direction of energy transfer.

In a transverse wave, the vibrations are at right angles to the direction of energy transfer. If the wave travels horizontally, the particles or disturbance move up and down. Examples include light waves, waves on a rope, and water surface waves as a simplified KS3 model.

In a longitudinal wave, the vibrations are parallel to the direction of energy transfer. This means the particles move backwards and forwards in the same direction that the wave energy travels. Sound is the key KS3 example. Longitudinal waves have compressions, where particles are close together, and rarefactions, where particles are spread out.

Feature	Transverse waves	Longitudinal waves
Direction of vibration	At right angles to energy transfer	Parallel to energy transfer
Main parts	Crests and troughs	Compressions and rarefactions
Examples	Light, rope waves, water surface waves	Sound, slinky compression waves
KS3 model phrase	Up-and-down disturbance travelling sideways	Squeeze-and-stretch disturbance travelling along

Describing a Wave

Scientists use specific words to describe waves. These words help us compare waves and explain what we observe.

Term	Meaning	Unit where relevant	Example
Wave	A disturbance that transfers energy without transferring matter overall	None	Sound travelling from a speaker to an ear
Medium	Material that a mechanical wave travels through	None	Air is the medium for sound in a classroom
Rest position	The normal position of a particle or point when no wave is passing	Metres for displacement if measured	The middle line on a wave diagram
Crest	Highest point of a transverse wave	None	The top of a rope wave
Trough	Lowest point of a transverse wave	None	The bottom of a rope wave
Compression	Region where particles are close together in a longitudinal wave	None	A squeezed part of a sound wave model
Rarefaction	Region where particles are spread out in a longitudinal wave	None	A stretched part of a sound wave model
Wavelength	Distance from one matching point on a wave to the next	Metres, m	Crest to next crest
Amplitude	Maximum displacement from the rest position	Metres, m, for many wave diagrams	Larger amplitude sound is louder
Frequency	Number of waves or vibrations per second	Hertz, Hz	300 vibrations per second = 300 Hz
Period	Time for one complete wave or vibration	Seconds, s	One vibration might take 0.01 s
Wave speed	How fast wave energy travels	Metres per second, m/s	Sound in air is about 340 m/s

Worked Example 1: Labelling a Transverse Wave

                         crest
                          ^
                          |
          wavelength      |                 direction of energy transfer
       <--------------->  |                         ------>
             /\           |           /\
            /  \          |          /  \
-----------/----\---------+---------/----\---------- rest position
          /      \        |        /      \
         /        \       |       /        \
        v          \      |      v
      trough        \     |    trough

                 amplitude
              <------------>
              from rest position
              to crest or trough

To label this diagram:

1. Find the rest position. This is the middle line through the wave.
2. Label a crest at the highest point.
3. Label a trough at the lowest point.
4. Measure wavelength from one crest to the next crest, or from one trough to the next trough. It must be between matching points.
5. Measure amplitude from the rest position to a crest or from the rest position to a trough. It is not the full height from trough to crest.

Worked Example 2: Labelling a Longitudinal Wave

Energy transfer direction  ------>

Compression       Rarefaction       Compression       Rarefaction
|||||||||||       | | | | |         |||||||||||       | | | |

<---------------- wavelength ---------------->
from one compression to the next compression

Particle vibration direction: <----> <----> <---->
particles move backwards and forwards parallel to energy transfer

To label this diagram:

1. Find compressions where the lines or particles are closest together.
2. Find rarefactions where the lines or particles are furthest apart.
3. Measure wavelength from the centre of one compression to the centre of the next compression, or from one rarefaction to the next rarefaction.
4. Add arrows showing that the particles vibrate backwards and forwards.
5. Add a separate arrow for the direction of energy transfer.

Summary: Wave Properties and What We Observe

Wave property	Meaning	What students may observe
Higher frequency	More vibrations each second	Higher pitch for sound
Lower frequency	Fewer vibrations each second	Lower pitch for sound
Larger amplitude	Greater maximum displacement	Louder sound or brighter light in simple KS3 terms
Smaller amplitude	Smaller maximum displacement	Quieter sound or dimmer light
Longer wavelength	Greater distance between matching points	Fewer waves fit into the same distance
Faster wave speed	Energy travels further each second	Shorter time to reach a detector

Frequency and amplitude are different properties. A high-pitched sound is not always loud. A loud sound is not always high-pitched.

Sound Waves

Sound waves are longitudinal mechanical waves. They are produced by vibrating objects. When a drum skin vibrates, it pushes and pulls the air particles next to it. This creates compressions and rarefactions in the air. These regions move outwards as a sound wave.

Sound can travel through solids, liquids, and gases because all of these contain particles that can vibrate. Sound usually travels faster in solids than in liquids, and faster in liquids than in gases, because particles are closer together in solids and can pass vibrations on quickly. Sound cannot travel through a vacuum because there are no particles to vibrate.

Vibrating speaker          Air particles                 Ear

   [SPEAKER]  ))))     |||||  | | |  |||||  | | |       (   )
      <-->             comp.  rare.  comp.  rare.        \_/

Sound energy transfer direction ------------------------>
Air particles vibrate backwards and forwards: <---->

Pitch and Frequency

Pitch describes how high or low a sound seems. A high-frequency sound has a high pitch. A low-frequency sound has a low pitch.

Human hearing is usually about 20 Hz to 20,000 Hz, although this varies between people and often changes with age. Ultrasound is sound with a frequency above the normal human hearing range. It can be used for medical scans, distance sensors, and cleaning delicate equipment. Infrasound is sound with a frequency below the normal human hearing range.

Loudness and Amplitude

Loudness depends mainly on amplitude. A larger-amplitude sound wave transfers more energy to the ear each second, so it sounds louder. A smaller-amplitude wave sounds quieter. Amplitude is not the same as frequency. A low-pitched drum can be loud, and a high-pitched whistle can be quiet.

Echoes

An echo is a reflected sound wave. When sound hits a hard surface, some of the sound energy is reflected back. Bats use echoes to locate insects. Ships use sonar to measure water depth. Some ultrasound sensors measure distance by timing how long an echo takes to return.

Worked Example 3: Frequency from Vibrations

A tuning fork makes 600 vibrations in 2 seconds.

Frequency means the number of vibrations each second.

Frequency = number of vibrations / time

Frequency = 600 / 2 = 300 Hz

The tuning fork has a frequency of 300 Hz.

Worked Example 4: Echo Distance as a Supported Challenge

Sound travels at about 340 m/s in air. An echo returns from a wall after 2 seconds.

The sound has travelled to the wall and back again, so the total journey time is for a two-way journey.

Total distance travelled by sound = speed x time

Total distance = 340 m/s x 2 s = 680 m

Distance to the wall = 680 m / 2 = 340 m

The wall is about 340 m away.

Light Waves

Light waves are transverse electromagnetic waves. They can travel through a vacuum, so light from the Sun can travel through space to Earth. Light travels in straight lines in a uniform material, such as air, clear water, or glass. A uniform material is one that is the same all the way through.

Light can be detected by the eye, cameras, and light sensors. It can also transfer energy to solar panels. Bright light transfers more energy to a detector each second than dim light.

Seeing Objects

Luminous objects give out their own light. Examples include the Sun, lamps, flames, and phone screens. Non-luminous objects do not give out their own visible light. We see them when light from a luminous object reflects from the object into our eyes.

The eye detects light. It does not send out sight rays.

Lamp                 Book                         Eye
 (*)  ----light----> [####] ----reflected light--> (o)

Arrows show the direction light travels.
The book is non-luminous, so it is seen by reflected light.

Transparent, Translucent, and Opaque Materials

Transparent materials transmit most light clearly, so you can see through them. Clear glass and clean water are examples.

Translucent materials transmit some light but scatter it, so objects cannot be seen clearly through them. Frosted glass and thin paper are examples.

Opaque materials do not transmit light through them. They absorb and reflect light, producing shadows. Wood, metal, and thick card are examples.

Material type	What happens to light	Example	Result
Transparent	Mostly transmitted with little scattering	Clear glass	You can see through it clearly
Translucent	Some transmitted, much scattered	Frosted glass	Light passes through but image is blurred
Opaque	Not transmitted; absorbed and reflected	Book, brick, metal	A shadow can form

Shadows

Shadows form when an opaque object blocks light. A sharp, dark central shadow is called the umbra. The size and sharpness of a shadow depend on the size of the light source and the distances between the source, object, and screen.

Point light source       Opaque object             Screen
       *                       [ ]                 |     |
      / \                     /   \                |shadow|
     /   \                   /     \               |umbra |
    /     \-----------------/-------\------------->|_____|

Light travels in straight lines.
The opaque object blocks some rays.

Colour

White light is a mixture of colours. A prism or raindrop can split white light into a spectrum. The visible spectrum is often remembered as red, orange, yellow, green, blue, indigo, and violet.

Objects appear coloured because they reflect some colours and absorb others. A red object in white light looks red because it reflects red light and absorbs many other colours. A coloured filter transmits some colours and absorbs others. For example, a red filter mainly transmits red light.

White light              Prism                  Spectrum
----------->            /    \             red
                       /      \            orange
                      /        \---------> yellow
                      \        /          green
                       \      /           blue
                        \____/            violet

Reflection of Light

Reflection happens when waves bounce off a surface. Light reflects from many surfaces, not only mirrors. Smooth, shiny surfaces can produce clear images because the reflected rays stay organised. Rough surfaces scatter reflected rays in many directions, so they do not form clear images.

In a ray diagram, a ray is a model that shows the direction light travels. It is not a physical thin line in space. Arrows show the direction of travel.

The normal is an imaginary line drawn at 90 degrees to the surface at the point where the ray hits. The angle of incidence is the angle between the incident ray and the normal. The angle of reflection is the angle between the reflected ray and the normal.

The law of reflection is:

Angle of incidence = angle of reflection

Reflection Ray Diagram

                         reflected ray
                              /
                             /  angle of reflection
                            /
                           /
                          /
                         |
                         | normal
                         |
-------------------------+-------------------- plane mirror
                         |
                        /
                       / angle of incidence
                      /
                     /
             incident ray

Both angles are measured from the normal, not from the mirror surface.

Worked Example 5: Drawing a Reflected Ray

1. Draw the plane mirror as a straight line.
2. Mark the point where the incident ray hits the mirror.
3. Draw the normal at 90 degrees to the mirror.
4. Measure or estimate the angle between the incident ray and the normal.
5. Draw the reflected ray on the other side of the normal with the same angle.
6. Add arrowheads to show the direction of light travel.
7. Label the incident ray, reflected ray, normal, angle of incidence, and angle of reflection.

If the angle of incidence is 35 degrees, the angle of reflection is also 35 degrees.

Regular and Diffuse Reflection

Regular reflection from a smooth surface

Incoming rays              Reflected rays
  \   \   \                   /   /   /
   \   \   \                 /   /   /
--------------------------- smooth surface

Diffuse reflection from a rough surface

Incoming rays              Reflected rays scatter
  \   \   \                   /  |   \
   \   \   \                 /   \    \
__/\/\____/\/\___/\____ rough surface

Each tiny part of a rough surface still obeys the law of reflection, but the tiny surface directions are different, so the reflected rays scatter.

Periscopes and Mirrors

A periscope uses two plane mirrors to reflect light into the eye. Simple periscopes can let someone see over an obstacle. Bathroom mirrors, car mirrors, reflective strips on school bags, and bicycle reflectors all depend on reflection. Reflective strips improve visibility because they send more light back towards drivers and cyclists.

Refraction of Light

Refraction is the change in direction when a wave crosses a boundary between materials because its speed changes. Light refracts when it passes between air, glass, and water. Sound can also refract in some situations, but light refraction is the main KS3 example.

When light enters glass from air, it slows down and usually bends towards the normal. When light leaves glass and enters air, it speeds up and usually bends away from the normal. In a rectangular glass block, the emergent ray is usually parallel to the incident ray but shifted sideways.

Air                         Glass block                         Air

incident ray
     \                         normal                      emergent ray
      \                          |                              \
       \                         |                               \
        \                        |                                \
---------\-----------------------+---------------------------------\-----
          \                      | refracted ray                   \
           \                     |                                  \
            \                    |                                   \
-------------\-------------------+------------------------------------\---
              \                  | normal

Entering glass: ray bends towards the normal.
Leaving glass: ray bends away from the normal.

Worked Example 6: Explaining Refraction Through a Glass Block

Light travels from air into glass. Its speed decreases, so the ray changes direction towards the normal. The ray then travels through the glass block in a straight line because the glass is uniform. When the ray leaves the glass and enters air, its speed increases, so it bends away from the normal. For a rectangular block, the ray that comes out is usually parallel to the original incident ray, but it has been shifted sideways.

Refraction in Everyday Life

A pencil can appear bent in a glass of water because light from the underwater part of the pencil refracts as it leaves the water and enters the air. The pencil has not actually bent. A swimming pool can look shallower than it really is because light from the bottom changes direction at the water-air boundary. Lenses use refraction to focus light. Glasses, cameras, magnifying glasses, and some telescopes use lenses. A prism uses refraction to split white light into colours because different colours change direction by different amounts.

Absorption and Transmission

When waves reach a boundary, they can be reflected, absorbed, or transmitted. Often more than one happens at the same time.

Process	Meaning	Light example	Sound example
Reflection	Wave bounces off a surface	Mirror reflecting light	Echo from a wall
Refraction	Wave changes direction at a boundary because speed changes	Light bending entering glass	Sound bending in layers of air, extension example
Absorption	Wave energy is taken in by a material	Black shirt absorbing light and warming up	Curtains absorbing sound
Transmission	Wave passes through a material	Light through a window	Sound through a thin wall

Black surfaces often absorb more visible light than white or shiny surfaces. Soft materials, such as curtains, carpets, foam panels, and ear defenders, can absorb sound energy and reduce noise.

The Electromagnetic Spectrum

Visible light is only one part of the electromagnetic spectrum. All electromagnetic waves are transverse waves. They can all travel through a vacuum and travel at the same speed in a vacuum. They differ in wavelength, frequency, and energy.

The order from longest wavelength and lowest frequency to shortest wavelength and highest frequency is:

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

Longest wavelength                                            Shortest wavelength
Lowest frequency                                               Highest frequency

Radio | Microwaves | Infrared | Visible | Ultraviolet | X-rays | Gamma rays
---------------------------------------------------------------------------->
                  increasing frequency and energy
<----------------------------------------------------------------------------
                  increasing wavelength

Wave type	Relative wavelength	Relative frequency	Common uses	Hazard or safety note
Radio waves	Longest	Lowest	Broadcasting, radio communication, TV signals	Strong signals can cause heating; equipment is controlled
Microwaves	Very long compared with light	Higher than radio	Cooking, mobile phone signals, satellite communication	Can heat body tissue; microwave ovens are shielded
Infrared	Longer than visible light	Lower than visible light	Remote controls, thermal cameras, heaters	Strong infrared can burn skin
Visible light	Middle of this table	Middle of this table	Seeing, photography, optical fibres	Very bright light or lasers can damage eyes
Ultraviolet	Shorter than visible light	Higher than visible light	Security marking, sterilising equipment	Can damage skin and eyes; sunscreen and goggles reduce risk
X-rays	Very short	Very high	Medical imaging, airport scanners	Ionising radiation can damage cells; exposure is limited and shielded
Gamma rays	Shortest	Highest	Sterilising medical equipment, cancer treatment	Very penetrating ionising radiation; strong safety controls needed

Radio waves are not sound waves. Radio waves are electromagnetic waves, not vibrations of air. Microwaves do not make food radioactive. They transfer energy to heat food. X-rays can be useful in medicine, but exposure is carefully controlled because they can damage living cells.

Sound Waves Compared with Light Waves

Feature	Sound waves	Light waves
Type of wave	Longitudinal	Transverse
Wave group	Mechanical	Electromagnetic
Need a medium?	Yes	No
Can travel through a vacuum?	No	Yes
Detected by	Ear, microphone, sound sensor	Eye, camera, light sensor
Produced by	Vibrating objects	Luminous objects, hot objects, electronic displays, lamps
Everyday example	Hearing a bell	Seeing a book
Important property link	Frequency affects pitch; amplitude affects loudness	Reflected light lets us see; intensity affects brightness

Real-World Examples

A guitar string vibrates when plucked. The vibration passes to the air as a longitudinal sound wave. The frequency affects pitch, while the amplitude affects loudness.

A drum skin vibrates when struck. A large-amplitude vibration produces a louder sound. A large drum often produces lower-frequency sounds than a small drum.

A speaker cone vibrates backwards and forwards. It creates compressions and rarefactions in the air that travel to an ear or microphone.

A student sees a book because light from a lamp reflects from the book into the eye. The light travels from the lamp to the book and then from the book to the eye.

A bathroom mirror forms a clear image because the smooth surface produces regular reflection.

A pencil looks bent in water because light refracts at the water-air boundary. The pencil has not actually changed shape.

A prism splits white light into colours because different colours refract by different amounts.

A bat sends out ultrasound and listens for echoes. The echo pattern gives information about insects and obstacles.

A ship uses sonar echoes to estimate the depth of water below it.

Fibre optic cables use light to carry information through thin glass fibres. At KS3, it is enough to know that light can carry information and can be guided along a cable.

Soft materials reduce noise because they absorb some sound energy instead of reflecting it strongly.

Working Scientifically with Waves

Good wave investigations need clear variables and careful measurements.

The independent variable is the variable you change. The dependent variable is the variable you measure. Control variables are kept the same to make the test fair.

Results should be repeatable. This means the same person can repeat the method and get similar results. Results should also be reliable. This means the evidence is trustworthy, often because repeats were taken, anomalies were checked, and averages were used. Accuracy means how close a measurement is to the true value. Precision means how close repeated measurements are to each other, often linked to the scale of the measuring instrument.

Practical Design Task: Sound Level and Distance

Plan an investigation into how the distance from a speaker affects sound level.

Investigation part	Example choice
Independent variable	Distance from speaker, in metres
Dependent variable	Sound level, in decibels, dB
Control variables	Same speaker, same volume setting, same sound frequency, same room, same sound meter, same background noise
Apparatus	Speaker, signal generator or phone tone app, metre ruler or tape measure, sound level meter, paper or spreadsheet
Safety	Keep volume at a safe level; avoid placing ears close to a loud speaker; keep cables tidy
Repeatability	Take at least three readings at each distance
Reliability	Calculate a mean, check anomalies, repeat in a quiet room
Improvement	Use a clamp stand to keep the sound meter at the same height and angle

Method:

1. Set the speaker to produce a steady tone at a safe volume.
2. Place the sound level meter 0.5 m from the speaker.
3. Record the sound level in dB.
4. Repeat the reading two more times.
5. Repeat for 1.0 m, 1.5 m, 2.0 m, and 2.5 m.
6. Calculate the mean sound level for each distance.
7. Plot a line graph with distance in metres on the x-axis and mean sound level in dB on the y-axis.
8. Look for a pattern and identify any anomaly.

Prediction: As distance from the speaker increases, the sound level will usually decrease because the sound energy spreads out over a larger area.

Accuracy, Precision, Anomalies, and Evaluation

An anomalous result does not fit the pattern. It might happen because of background noise, a movement of the sound meter, a different volume setting, or a reading error. A good evaluation identifies possible errors and suggests realistic improvements.

Good improvements include:

• repeat readings and calculate a mean,
• use the same apparatus throughout,
• measure distances carefully from the same point on the speaker,
• reduce background noise,
• use a darkened room for light experiments,
• use a protractor carefully for ray diagrams,
• draw thin pencil lines so angles can be measured accurately,
• check that a ray box is not too bright and does not shine into eyes.

Data and Skills Tasks

Task 1: Sound Frequency and Pitch

Sound source	Frequency (Hz)
Large drum	80
Guitar string	196
Tuning fork A	256
Tuning fork B	512
Whistle	4,000
Ultrasound distance sensor	40,000
Infrasound vibration	10

Questions:

1. Which sound has the highest pitch?
2. Which sound has the lowest pitch?
3. Which sounds are outside the usual human hearing range of about 20 Hz to 20,000 Hz?
4. Explain why the 512 Hz tuning fork has a higher pitch than the 256 Hz tuning fork.

Task 2: Oscilloscope Trace Comparison

Each trace shows the same amount of time.

Trace A: high frequency, small amplitude
  /\  /\  /\  /\  /\
 /  \/  \/  \/  \/  \

Trace B: low frequency, large amplitude
      /\          /\
     /  \        /  \
____/    \______/    \____

Trace C: medium frequency, medium amplitude
   /\    /\    /\
__/  \__/  \__/  \__

Questions:

1. Which trace has the highest frequency?
2. Which trace is loudest if these are sound waves?
3. Which trace has the highest pitch but is not the loudest?
4. Correct this statement: "Trace B has the highest pitch because it has the largest amplitude."

Task 3: Reflection Results Table

Students measured angles for light reflecting from a plane mirror.

Test	Angle of incidence (degrees)	Angle of reflection (degrees)
1	10	11
2	20	20
3	30	29
4	40	58
5	50	51
6	60	60

Questions:

1. Describe the pattern in the results.
2. Which result is anomalous?
3. Write a conclusion using the law of reflection.
4. Suggest one reason for the anomalous result.
5. Suggest one improvement to make the angle measurements more accurate.

Task 4: Refraction Practical Data

Light enters a glass block from air.

Incident angle in air (degrees)	Refracted angle in glass (degrees)
10	7
20	13
30	19
40	25
50	31
60	35

Questions:

1. What happens to the refracted angle as the incident angle increases?
2. Is the refracted angle in glass larger or smaller than the incident angle in air?
3. Explain this pattern using speed change at a boundary.
4. Which variables should be controlled in this investigation?

Task 5: Shadow Investigation

A student changes the distance between a light source and an opaque object. The screen stays 60 cm behind the object.

Distance from light source to object (cm)	Shadow height on screen (cm)
10	24
20	15
30	12
40	10
50	9

Questions:

1. Identify the independent variable.
2. Identify the dependent variable.
3. Name two control variables.
4. What type of graph should be drawn?
5. What should go on the x-axis and y-axis, including units?
6. Describe the pattern in the data.
7. Explain why the shadow changes size.

Task 6: Absorption Investigation

A speaker is placed behind different materials. A sound level meter is placed 1 m away.

Material between speaker and meter	Mean sound level (dB)
No material	70
Thin paper	66
Cotton curtain	58
Foam panel	50
Wooden board	62

Questions:

1. Which material transmits the most sound?
2. Which material absorbs or blocks the most sound?
3. Use data to support your answer.
4. How could the student improve reliability?
5. Why should the same speaker volume be used each time?

Task 7: Electromagnetic Spectrum Information

Use the electromagnetic spectrum table in this pack.

Questions:

1. Which wave type has the longest wavelength?
2. Which wave type has the highest frequency?
3. Name one use of infrared.
4. Name one safety precaution linked to ultraviolet.
5. Put these in order from lowest frequency to highest frequency: visible light, radio waves, gamma rays, microwaves.

Graph Skill: Angle of Incidence Against Angle of Reflection

For the reflection results table, a suitable graph is a line graph or scatter graph because both variables are numerical. Put angle of incidence in degrees on the x-axis. Put angle of reflection in degrees on the y-axis. A best-fit line should show that the angle of reflection increases as the angle of incidence increases. Most points should be close to the line y = x. The result for 40 degrees incidence and 58 degrees reflection is an anomaly because it does not fit the pattern.

When drawing a graph:

• label both axes with units,
• use an even scale,
• plot points carefully,
• draw a sensible best-fit line if the pattern is continuous,
• circle or note anomalies,
• write a conclusion that uses evidence from the graph.

Common Misconceptions

Wrong idea	Correct idea	Quick example
Sound can travel through space	Sound needs particles in a medium, so it cannot travel through a vacuum	Astronauts use radios, not direct sound through space
All waves require a medium	Mechanical waves need a medium, but electromagnetic waves can travel through a vacuum	Light from the Sun travels through space
Waves carry matter from source to receiver	Waves transfer energy; particles usually vibrate around fixed positions	Air particles vibrate but do not travel from a speaker to your ear
Light travels from the eye to the object	Light enters the eye from luminous objects or after reflection	You see a book when lamp light reflects from it into your eye
A ray diagram shows real thin lines of light	Rays are models showing direction	Arrows on rays show travel direction
Reflection only happens from mirrors	Most surfaces reflect some light	Paper reflects light diffusely so you can see it
Rough surfaces do not obey the law of reflection	Each tiny part obeys the law, but rays scatter	Rough paper gives diffuse reflection
Refraction happens because light curves by itself	Light changes direction at a boundary because speed changes	Light bends entering glass from air
A pencil actually bends in water	It appears bent because light refracts	The pencil is still straight when removed
Higher amplitude means higher pitch	Higher amplitude means louder sound; higher frequency means higher pitch	A loud drum can have low pitch
Higher frequency means louder sound	Frequency affects pitch, not loudness	A quiet whistle can be high-pitched
Wavelength is the height of a wave	Wavelength is the distance between matching points; amplitude is height from rest	Crest-to-crest distance is wavelength
The electromagnetic spectrum is only visible light	Visible light is one small part of a wider spectrum	Radio waves and X-rays are also electromagnetic
Radio waves are sound waves	Radio waves are electromagnetic waves	Radio aerials detect electromagnetic signals
Microwaves always make things radioactive	Microwaves heat food but do not make it radioactive	Microwave ovens are shielded to stop leakage
X-rays are safe because doctors use them	X-rays can damage cells, so exposure is controlled	Radiographers use shielding and limited doses

Key Vocabulary

Term	Meaning	Unit where relevant	Example
Absorption	Taking in wave energy	None	Black fabric absorbing light
Amplitude	Maximum displacement from the rest position	m for displacement	Larger amplitude sound is louder
Angle of incidence	Angle between incident ray and normal	degrees	40 degrees
Angle of reflection	Angle between reflected ray and normal	degrees	40 degrees if incidence is 40 degrees
Compression	Region of a longitudinal wave where particles are close together	None	Compression in a sound wave
Diffuse reflection	Scattering of reflected rays from a rough surface	None	Light reflecting from paper
Electromagnetic wave	Wave that can travel through a vacuum	None	Visible light
Frequency	Number of waves or vibrations per second	hertz, Hz	512 Hz tuning fork
Incident ray	Ray travelling towards a surface	None	Ray hitting a mirror
Longitudinal wave	Wave with vibrations parallel to energy transfer	None	Sound
Medium	Material a mechanical wave travels through	None	Air for sound
Normal	Line drawn at 90 degrees to a surface	None	Used to measure reflection angles
Opaque	Does not transmit light	None	Brick wall
Ray	Model showing direction light travels	None	Arrow in a ray diagram
Rarefaction	Region of a longitudinal wave where particles are spread out	None	Spread-out part of a sound wave
Reflected ray	Ray travelling away after reflection	None	Ray leaving a mirror
Reflection	Wave bouncing off a surface	None	Echo or mirror reflection
Refraction	Change in direction at a boundary because speed changes	None	Light entering glass
Transmission	Passing through a material	None	Light through a window
Transparent	Transmits light clearly	None	Clear glass
Translucent	Transmits and scatters light	None	Frosted glass
Transverse wave	Wave with vibrations at right angles to energy transfer	None	Light
Vacuum	Space with no particles	None	Space is close to a vacuum
Wave speed	Speed at which wave energy travels	m/s	Sound in air about 340 m/s
Wavelength	Distance between matching points on a wave	m	Crest to crest

Exam-Style Questions

Multiple Choice Questions

1. Which statement best describes a wave? A. A stream of particles moving from source to receiver
   B. A disturbance that transfers energy without transferring matter overall
   C. A force that only travels through air
   D. A line drawn in a ray diagram

2. Which wave can travel through a vacuum? A. Sound
   B. A slinky compression wave
   C. Visible light
   D. A water surface wave

3. Sound is best described as: A. a transverse electromagnetic wave
   B. a longitudinal mechanical wave
   C. a transverse mechanical wave only found in solids
   D. a ray of light

4. A student hears a higher pitch when: A. frequency increases
   B. amplitude increases
   C. wavelength is labelled vertically
   D. the sound becomes dimmer

5. A louder sound usually has: A. lower frequency
   B. higher frequency
   C. larger amplitude
   D. no wavelength

6. In reflection, angles are measured from: A. the mirror surface
   B. the normal
   C. the reflected ray only
   D. the edge of the paper

7. A ray of light has an angle of incidence of 25 degrees on a plane mirror. The angle of reflection is: A. 0 degrees
   B. 25 degrees
   C. 50 degrees
   D. 90 degrees

8. Refraction happens when: A. light changes direction at a boundary because its speed changes
   B. sound travels through a vacuum
   C. rays leave the eye and hit an object
   D. wavelength is measured from trough to crest

9. Which list is in the correct electromagnetic spectrum order from lowest frequency to highest frequency? A. Gamma rays, X-rays, visible light, radio waves
   B. Radio waves, microwaves, infrared, visible light
   C. Visible light, infrared, microwaves, radio waves
   D. Ultraviolet, visible light, infrared, radio waves

10. A non-luminous object is seen because: A. it sends sight rays to the eye
    B. it always gives out visible light
    C. light reflects from it into the eye
    D. sound waves reflect from it into the eye

Fill-in-the-Blank Questions

Use these words: amplitude, compression, electromagnetic, frequency, longitudinal, medium, normal, rarefaction, reflection, refraction, transverse, wavelength.

1. The distance from one crest to the next crest is called the __________.
2. The number of vibrations per second is called __________.
3. Sound is a __________ wave because the vibrations are parallel to the direction of energy transfer.
4. Light is a __________ wave because its vibrations are at right angles to the direction of energy transfer.
5. A mechanical wave needs a __________ to travel through.
6. A region where particles are close together in a sound wave is a __________.
7. A region where particles are spread out in a sound wave is a __________.
8. Waves bouncing off a surface is called __________.
9. A change in direction at a boundary because wave speed changes is called __________.
10. The line drawn at 90 degrees to a mirror surface is the __________.

Short Answer Questions

1. Explain why sound cannot travel through space.
2. Describe the difference between a mechanical wave and an electromagnetic wave.
3. Compare a transverse wave and a longitudinal wave.
4. State the law of reflection.
5. Explain why rough paper can be seen even though it is not a mirror.
6. Explain why a pencil appears bent in a glass of water.
7. Describe how an opaque object makes a shadow.
8. Explain the difference between transparent and translucent materials.
9. Give one use and one hazard of ultraviolet radiation.
10. Explain why radio waves are not sound waves.

Diagram Labelling Questions

1. Draw and label a transverse wave. Include crest, trough, rest position, amplitude, wavelength, and direction of energy transfer.
2. Draw and label a longitudinal wave. Include compression, rarefaction, wavelength, particle vibration direction, and energy transfer direction.
3. Draw a ray diagram for a plane mirror with an incident ray at 40 degrees to the normal. Label the normal, incident ray, reflected ray, angle of incidence, and angle of reflection.
4. Draw a simple diagram showing how a lamp lets a student see a non-luminous book.
5. Draw a simple shadow diagram with a light source, opaque object, screen, and umbra.

Calculation Questions

1. A string vibrates 900 times in 3 seconds. Calculate its frequency.
2. A speaker cone vibrates 1,200 times in 4 seconds. Calculate the frequency of the sound.
3. A student hears an echo 1.5 seconds after clapping. Sound travels at about 340 m/s. Calculate the approximate distance to the wall. Remember the sound travels to the wall and back.
4. A tuning fork vibrates at 256 Hz. How many vibrations does it make in 5 seconds?

Practical and Data Questions

1. In a reflection experiment, name the independent variable and dependent variable.
2. Why should students repeat each angle measurement in a reflection experiment?
3. In a sound absorption investigation, why should the same speaker volume and distance be used each time?
4. A graph shows that sound level decreases as distance from a speaker increases. Write a conclusion using this pattern.
5. A student gets one result that does not fit the pattern. What is this type of result called, and what should the student do?
6. Give two safety precautions for using a ray box or bright light source.
7. Explain how to improve the precision of angle measurements in a ray diagram practical.

Longer 6-8 Mark Question

Compare sound waves and light waves. Include wave type, whether each needs a medium, whether each can travel through a vacuum, how each is produced, how each is detected, and one everyday example for each. Use scientific vocabulary.

Model Answers

Multiple Choice Answers

1. B. A wave transfers energy without transferring matter overall.
2. C. Visible light is an electromagnetic wave, so it can travel through a vacuum.
3. B. Sound is a longitudinal mechanical wave.
4. A. Higher frequency means higher pitch.
5. C. Larger amplitude usually means louder sound.
6. B. Reflection angles are measured from the normal.
7. B. The law of reflection says the angles are equal.
8. A. Refraction is caused by a speed change at a boundary.
9. B. Radio waves have lower frequency than microwaves, infrared, and visible light.
10. C. Non-luminous objects are seen when reflected light enters the eye.

Fill-in-the-Blank Answers

1. wavelength
2. frequency
3. longitudinal
4. transverse
5. medium
6. compression
7. rarefaction
8. reflection
9. refraction
10. normal

Short Answer Model Answers

1. Sound cannot travel through space because sound is a mechanical wave and needs particles in a medium to vibrate. A vacuum has no particles, so sound energy cannot be passed on.
2. A mechanical wave needs a material medium, such as air or water. An electromagnetic wave can travel through a vacuum. Sound is mechanical, while light is electromagnetic.
3. In a transverse wave, vibrations are at right angles to the direction of energy transfer. In a longitudinal wave, vibrations are parallel to the direction of energy transfer. Light is transverse and sound is longitudinal.
4. The law of reflection states that the angle of incidence equals the angle of reflection. Both angles are measured from the normal.
5. Rough paper reflects light diffusely. Each tiny part reflects light, but the rays scatter in different directions, so the paper can be seen without forming a clear mirror image.
6. A pencil appears bent in water because light from the underwater part changes direction when it crosses from water into air. This refraction changes where the light seems to have come from.
7. A shadow forms when an opaque object blocks light travelling in straight lines. The region behind the object receives less light.
8. A transparent material transmits light clearly, so objects can be seen through it. A translucent material transmits some light but scatters it, so images look blurred.
9. Ultraviolet can be used for security marking or sterilising equipment. It can damage skin and eyes, so protection such as sunscreen, clothing, or goggles may be needed.
10. Radio waves are electromagnetic waves that can travel through a vacuum. Sound waves are mechanical vibrations of particles, so radio waves are not sound waves.

Calculation Model Answers

1. Frequency = 900 vibrations / 3 s = 300 Hz.
2. Frequency = 1,200 vibrations / 4 s = 300 Hz.
3. Total sound distance = 340 m/s x 1.5 s = 510 m. This is there and back, so distance to wall = 510 m / 2 = 255 m.
4. Number of vibrations = frequency x time = 256 Hz x 5 s = 1,280 vibrations.

Data Task Model Answers

Sound frequency and pitch:

1. The ultrasound distance sensor has the highest frequency, so it has the highest pitch if it could be heard.
2. The infrasound vibration has the lowest frequency.
3. The ultrasound sensor at 40,000 Hz is above the usual human hearing range. The infrasound vibration at 10 Hz is below the usual human hearing range.
4. The 512 Hz tuning fork makes more vibrations each second than the 256 Hz tuning fork, so it has a higher frequency and higher pitch.

Oscilloscope traces:

1. Trace A has the highest frequency because it shows the most waves in the same time.
2. Trace B is loudest because it has the greatest amplitude.
3. Trace A has the highest pitch but is not the loudest.
4. Corrected statement: Trace B has the largest amplitude, so it is the loudest. It does not have the highest pitch because it has a low frequency.

Reflection table:

1. The angle of reflection is usually about equal to the angle of incidence.
2. Test 4 is anomalous because 40 degrees incidence gives 58 degrees reflection, which does not fit the pattern.
3. The results support the law of reflection because most angle pairs are equal or almost equal.
4. The anomalous result may have been caused by reading the protractor wrongly, drawing a thick ray, moving the mirror, or measuring from the mirror instead of the normal.
5. Use a sharp pencil, a clear protractor, repeat measurements, and measure angles from the normal.

Refraction table:

1. The refracted angle increases as the incident angle increases.
2. The refracted angle in glass is smaller than the incident angle in air.
3. The ray bends towards the normal when it enters glass from air because light slows down in glass.
4. Control variables include the same glass block, same ray box, same colour of light if possible, same boundary, same method for measuring angles, and same room lighting.

Shadow investigation:

1. The independent variable is the distance from the light source to the object.
2. The dependent variable is the shadow height on the screen.
3. Control variables include the same object, same light source, same screen distance, same screen, and same room lighting.
4. A line graph is suitable because both variables are numerical and continuous.
5. The x-axis should be distance from light source to object in cm. The y-axis should be shadow height in cm.
6. As the object is moved further from the light source, the shadow height decreases.
7. Light travels in straight lines. When the object is closer to the source, it blocks a wider spread of rays, so the shadow is larger.

Absorption investigation:

1. Thin paper transmits the most sound out of the materials because the sound level is highest with a material, at 66 dB.
2. The foam panel absorbs or blocks the most sound because the mean sound level is lowest, at 50 dB.
3. Compared with no material at 70 dB, the foam panel reduces the sound level to 50 dB, a decrease of 20 dB.
4. Repeat each reading, calculate means, keep background noise low, and use the same distances and volume.
5. The same volume is needed so the material is the only variable affecting the sound level.

Electromagnetic spectrum:

1. Radio waves have the longest wavelength.
2. Gamma rays have the highest frequency.
3. Infrared can be used in remote controls or thermal cameras.
4. A safety precaution for ultraviolet is to protect skin and eyes using sunscreen, clothing, shade, or goggles.
5. Radio waves, microwaves, visible light, gamma rays.

Longer Question Model Answer

Sound waves and light waves both transfer energy from a source to a detector, but they are different types of wave. Sound is a longitudinal mechanical wave. The particles vibrate parallel to the direction of energy transfer, producing compressions and rarefactions. Sound needs a medium, such as air, water, or a solid, so it cannot travel through a vacuum. Sound is produced by vibrating objects, such as a speaker cone, guitar string, or tuning fork. It is detected by the ear, a microphone, or a sound sensor. An everyday example is hearing music from a loudspeaker.

Light is a transverse electromagnetic wave. Its vibrations are at right angles to the direction of energy transfer. Light does not need a material medium, so it can travel through a vacuum. This is why light from the Sun can travel through space to Earth. Light is produced by luminous objects, such as the Sun, lamps, flames, and screens. It is detected by the eye, cameras, or light sensors. An everyday example is seeing a non-luminous book when light from a lamp reflects from the book into the eye.

A similarity is that both sound and light can reflect. Sound reflection can produce echoes, while light reflection allows mirrors and helps us see objects. A key difference is that sound cannot travel through space, but light can.

Revision Checklist

Use this checklist to check your understanding.

• I can define a wave as a disturbance that transfers energy without transferring matter overall.
• I can explain the difference between a source, receiver, and detector.
• I can describe the difference between mechanical waves and electromagnetic waves.
• I can explain why sound needs a medium and cannot travel through a vacuum.
• I can explain why light can travel through space.
• I can compare transverse and longitudinal waves using vibration direction and energy transfer direction.
• I can label crest, trough, rest position, amplitude, and wavelength on a transverse wave.
• I can label compression, rarefaction, wavelength, vibration direction, and energy transfer direction on a longitudinal wave.
• I can state that frequency is measured in hertz, Hz.
• I can calculate frequency using number of vibrations divided by time.
• I can explain that higher frequency means higher pitch.
• I can explain that larger amplitude means louder sound.
• I can avoid confusing pitch with loudness.
• I can describe how a vibrating object produces sound.
• I can explain echoes as reflected sound waves.
• I can describe ultrasound and infrasound.
• I can explain how luminous and non-luminous objects are seen.
• I can draw arrows in the correct direction from light source to object to eye.
• I can explain how shadows form.
• I can describe transparent, translucent, and opaque materials.
• I can explain reflection using incident ray, reflected ray, normal, angle of incidence, and angle of reflection.
• I can use the law of reflection.
• I can explain the difference between regular and diffuse reflection.
• I can explain refraction as a change in direction at a boundary because wave speed changes.
• I can describe light bending towards the normal entering glass from air and away from the normal leaving glass into air.
• I can explain why a pencil appears bent in water.
• I can describe white light as a mixture of colours.
• I can explain how coloured filters and coloured objects work in simple terms.
• I can list the electromagnetic spectrum in order from radio waves to gamma rays.
• I can link electromagnetic waves to uses and hazards.
• I can identify independent, dependent, and control variables in a wave investigation.
• I can explain fair testing, repeatability, reliability, accuracy, precision, anomalies, and improvements.
• I can interpret results tables and graphs for wave investigations.
• I can write conclusions that use evidence and scientific reasoning.