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KS3 Science · Year 9Chapter 13 · Waves and the electromagnetic spectrum
Year 9 · Chapter 13

Waves and the electromagnetic spectrum

By the end of this chapter you will be able to

  • Distinguish transverse and longitudinal waves, with examples
  • Name and measure amplitude, wavelength, frequency and period
  • Use v = f x lambda and T = 1 / f in simple calculations
  • Explain how waves transfer energy and information without transferring matter
  • Order the electromagnetic spectrum, and link each part to a use and a hazard

You should already know

  • Light and sound waves (Year 8 Science, Chapter 12)
  • Speed, distance and time (Year 7 Science, Chapter 11)

Where this leads

  • Every topic in Year 9 physics uses energy transfer, and this chapter completes the physics strand

National Curriculum for England, Key Stage 3 science, Year 9. Content: 9P6 transverse and longitudinal waves: amplitude, wavelength, frequency and period, in metres, hertz and seconds, 9P6 the wave equation v = f x lambda in simple cases, 9P6 waves transfer energy and information without transferring matter, 9P6 the electromagnetic spectrum in depth: order by wavelength and frequency; uses and hazards explained through energy per photon (basic), 9P6 all electromagnetic waves travel at the same speed in a vacuum (deepens Year 8, Chapter 12).

Exercise P  Do you remember?

1
FWhat is the name for light and sound energy travelling through space or matter? Write the word.
2
FWhat is 4 x 2.5? Write the number.
3
FWhat is the speed of light in a vacuum, approximately, in metres per second? Write the number, to one significant figure, as 3 x 10 to the power 8.
4
FWhat is the unit of frequency? Write the symbol.
5
FWhat is 12 divided by 4? Write the number.
13.1

Transverse and longitudinal waves

Year 9
9P6: transverse and longitudinal waves
Video lesson: Transverse and longitudinal wavesComing soon
Story. A pupil flicks one end of a rope up and down, and a wave travels along it. A second pupil pushes and pulls a long spring, and squashed and stretched regions travel along the spring. The teacher asks which wave is transverse, and which is longitudinal.

In a transverse wave, the particles vibrate at right angles to the direction the energy travels. Water waves, light and other electromagnetic waves are transverse. In a longitudinal wave, the particles vibrate parallel to the direction of energy transfer. Sound waves are longitudinal, with compressions and rarefactions.

amplitudewavelength (crest to crest)transverse: vibration at right angles to the direction of energy transfer
A transverse wave, with its amplitude and wavelength labelled
longitudinal: vibration parallel to the direction of energy transfercompressions (crowded) and rarefactions (spread out) travel along the row
A longitudinal wave shown as compressions and rarefactions

Key ideas

  • Transverse: vibration at right angles to the direction of travel.
  • Longitudinal: vibration parallel to the direction of travel.
  • Water waves and light are transverse; sound is longitudinal.
  • Compressions and rarefactions are the features of a longitudinal wave.
Worked example 13.1.1
Are water waves transverse or longitudinal? Write the word.

Method. Think about how the water moves.

  1. Look. Water particles move up and down, at right angles to the wave.
    up and down
  2. Name it. So water waves are transverse.
    transverse
  3. Write the answer.
    transverse

Check. The wave travels across the surface. ✓

Worked example 13.1.2
Is sound transverse or longitudinal? Write the word.

Method. Recall the features of sound.

  1. Recall. Sound has compressions and rarefactions along the direction of travel.
    compressions and rarefactions
  2. Name it. So sound is longitudinal.
    longitudinal
  3. Write the answer.
    longitudinal

Check. The particles vibrate along the direction of travel. ✓

Worked example 13.1.3
Which of these is a longitudinal wave: light, or a sound wave? Write the words.

Method. Recall which wave is longitudinal.

  1. Recall. Light is a transverse wave.
    transverse
  2. Name it. So the sound wave is the longitudinal one.
    sound wave
  3. Write the answer.
    sound wave

Check. Light is an electromagnetic transverse wave. ✓

Watch out

Watch out: a wave does not carry the particles along with it. The particles only vibrate about a fixed position.

Exam tip

Exam tip. Describe the vibration relative to the direction of travel, using the words “at right angles” or “parallel”.

Try it (with your teacher, or a grown-up at home). With your teacher, tie one end of a long soft spring to a fixed point. Flick one end side to side to make a transverse wave, then push and pull it along to make a longitudinal wave. Say which way the coils vibrate in each case.

Exercise 13A  Transverse and longitudinal waves

1
FIn a transverse wave, are the particles vibrating at right angles or parallel to the direction of energy transfer? Write the words.
2
FIn a longitudinal wave, are the particles vibrating at right angles or parallel to the direction of energy transfer? Write the words.
3
FName the two regions of a longitudinal wave: crowded and spread out. Write the words for the crowded region.
4
FIs light a transverse or a longitudinal wave? Write the word.
5
FIs sound a transverse or a longitudinal wave? Write the word.
6
FDo the particles of a wave travel with the wave along the direction of travel? Write yes or no.
7
PSWhich kind of wave has crests and troughs: transverse or longitudinal? Write the word.
8
PSIn a row of particles, a region is crowded. Is it a compression or a rarefaction? Write the word.
9
PSA sound wave travels from a speaker to your ear. Do the air particles travel to your ear? Write yes or no.
10
RExplain why a transverse wave on a rope looks like it is moving along, although the rope does not. Write one sentence. Accept any sentence saying the pulse of energy moves along the rope, while each part only moves up and down.
11
RChallenge: a pupil says both transverse and longitudinal waves need particles to vibrate. Is this always correct? Write yes or no, and give one reason in one sentence. Accept no, because light (transverse) travels through a vacuum where there are no particles.
13.2

Amplitude, wavelength, frequency and period

Year 9
9P6: amplitude, wavelength, frequency and period, in metres, hertz and seconds
Video lesson: Amplitude, wavelength, frequency and periodComing soon
Story. A pupil counts the crests of a wave passing a point in 10 seconds: 40 crests go past. She writes down the frequency, and asks how long one wave takes to pass, which is the period.

Amplitude is the maximum displacement of the wave from its rest position. Wavelength is the distance from one crest to the next (or from one compression to the next). Frequency is the number of waves passing a point each second, measured in hertz, Hz. Period is the time for one full wave to pass a point, measured in seconds.

The period and frequency are linked by T = 1 / f: the period is one divided by the frequency, and the frequency is one divided by the period.

QuantitySymbolUnitMeaning
amplitude-mmaximum displacement from rest
wavelengthlambdamdistance from one crest to the next
frequencyfHznumber of waves passing a point each second
periodTstime for one full wave to pass a point
wave speedvm/sdistance travelled per second
Amplitude, wavelength, frequency and period, with their units

Key ideas

  • Amplitude: maximum displacement from rest, in metres.
  • Wavelength: crest to crest, in metres.
  • Frequency: waves per second, in hertz (Hz).
  • Period: time for one wave, in seconds; T = 1 / f.
Worked example 13.2.1
In 10 seconds, 40 waves pass a point. What is the frequency, in hertz? Write the number.

Method. Frequency = number of waves / time.

  1. Divide. 40 / 10 = 4.
    40 / 10
  2. Conclude. So the frequency is 4 Hz.
    4
  3. Write the answer.
    4

Check. 4 waves per second. ✓

Worked example 13.2.2
A wave has a frequency of 20 Hz. What is its period, in seconds? Write the number.

Method. Use T = 1 / f.

  1. Write. T = 1 / 20.
    1 / 20
  2. Calculate. So the period is 0.05 s.
    1 / 20 = 0.05
  3. Write the answer.
    0.05

Check. 20 x 0.05 = 1. ✓

Worked example 13.2.3
A wave has a period of 0.5 s. What is its frequency, in hertz? Write the number.

Method. Use f = 1 / T.

  1. Write. f = 1 / 0.5.
    1 / 0.5
  2. Calculate. So the frequency is 2 Hz.
    1 / 0.5 = 2
  3. Write the answer.
    2

Check. 2 x 0.5 = 1. ✓

Watch out

Watch out: amplitude is not the wavelength. Amplitude is the height from rest to a crest; wavelength is crest to crest.

Exam tip

Exam tip. Frequency is in hertz, period is in seconds. Use T = 1 / f to switch between them.

Try it (with your teacher, or a grown-up at home). With your teacher, use a ripple tank or a bowl of water and a finger. Tap at a steady rate for 10 seconds and count the waves that pass a point. Work out the frequency and the period.

Exercise 13B  Amplitude, wavelength, frequency and period

1
FWhat is the unit of frequency? Write the word.
2
FWhat is the unit of period? Write the word.
3
FWhat is the name of the maximum displacement of a wave from its rest position? Write the word.
4
FWhat is the distance from one crest to the next called? Write the word.
5
FWhat is the frequency of a wave that has 5 waves passing each second? Write the number, in Hz.
6
PSIn 10 seconds, 40 waves pass a point. What is the frequency, in hertz? Write the number.
7
PSA wave has a frequency of 2 Hz. What is its period, in seconds? Write the number.
8
PSA wave has a frequency of 20 Hz. What is its period? Write the number, in seconds.
9
PSA wave has a period of 0.25 s. What is its frequency, in hertz? Write the number.
10
PSA wave has a period of 2 s. How many waves pass a point in 10 s? Write the number.
11
PSWhich is larger: the amplitude or the wavelength of a wave, when a wave is drawn with its crest at 1 cm high and crests 4 cm apart? Write the word.
12
RExplain why the period is the inverse of the frequency. Write one sentence. Accept any sentence saying one wave takes one period, so the number of waves each second is one divided by that time.
13
RChallenge: a wave has 60 waves passing a point in 20 s. Find the period, in seconds. Write the number.
13.3

The wave equation: v = f x lambda

Year 9
9P6: the wave equation v = f x lambda in simple cases
Video lesson: The wave equation: v = f x lambdaComing soon
Story. A ripple tank makes waves with a wavelength of 4 cm. The teacher asks the class to find how fast the waves travel, if the frequency is 5 Hz. The class uses the wave equation to find the speed.

The wave equation links the speed of a wave to its frequency and wavelength: v = f x lambda, where v is the speed in metres per second, f is the frequency in hertz and lambda is the wavelength in metres. It can be rearranged to f = v / lambda or lambda = v / f.

Key ideas

  • Wave equation: v = f x lambda.
  • Speed in metres per second; frequency in hertz; wavelength in metres.
  • Rearrange: f = v / lambda, lambda = v / f.
  • Change centimetres to metres before using the equation.
Worked example 13.3.1
A wave has a frequency of 50 Hz and a wavelength of 4 m. What is its speed, in m/s? Write the number.

Method. Use v = f x lambda.

  1. Write. v = 50 x 4.
    50 x 4
  2. Calculate. So the speed is 200 m/s.
    50 x 4 = 200
  3. Write the answer.
    200

Check. 200 / 50 = 4 m. ✓

Worked example 13.3.2
A wave travels at 300 m/s with a wavelength of 3 m. What is its frequency, in Hz? Write the number.

Method. Use f = v / lambda.

  1. Write. f = 300 / 3.
    300 / 3
  2. Calculate. So the frequency is 100 Hz.
    300 / 3 = 100
  3. Write the answer.
    100

Check. 100 x 3 = 300 m/s. ✓

Worked example 13.3.3
A ripple tank makes waves with a wavelength of 4 cm at a frequency of 5 Hz. Find the speed, in cm/s. Write the number.

Method. Use v = f x lambda in cm.

  1. Write. v = 5 x 4.
    5 x 4
  2. Calculate. So the speed is 20 cm/s.
    5 x 4 = 20
  3. Write the answer.
    20

Check. 20 / 4 = 5 Hz. ✓

Watch out

Watch out: keep the units consistent. A wavelength in centimetres gives a speed in centimetres per second.

Exam tip

Exam tip. Write v = f x lambda, substitute the three values with their units, then calculate. Check the unit of your answer.

Try it (with your teacher, or a grown-up at home). With your teacher, use a ripple tank or a bowl of water. Count the waves that pass a point each second to find the frequency, and measure the distance between two crests to find the wavelength. Calculate the speed of the ripples.

Exercise 13C  The wave equation: v = f x lambda

1
FWrite the wave equation linking speed, frequency and wavelength. Write the symbols.
2
FWhat is the unit of wavelength in the wave equation? Write the word.
3
FWhat is the unit of the speed in the wave equation? Write the symbol.
4
FRearrange v = f x lambda to find the frequency. Write the equation.
5
PSA wave has a frequency of 50 Hz and a wavelength of 4 m. What is its speed, in m/s? Write the number.
6
PSA wave travels at 300 m/s and has a wavelength of 3 m. What is its frequency, in Hz? Write the number.
7
PSA wave travels at 340 m/s and has a frequency of 85 Hz. What is its wavelength, in m? Write the number.
8
PSA wave has a frequency of 10 Hz and a wavelength of 0.5 m. What is its speed, in m/s? Write the number.
9
PSA wave travels at 20 m/s with a frequency of 4 Hz. What is its wavelength, in m? Write the number.
10
PSIn a ripple tank, the wavelength is 4 cm and the frequency is 5 Hz. What is the speed, in cm/s? Write the number.
11
PSA wave has a speed of 300 m/s and a frequency of 150 Hz. Find the wavelength, in m. Write the number.
12
RExplain why doubling the frequency of a wave, at the same speed, halves its wavelength. Write one sentence. Accept any sentence saying the speed is fixed, so the wavelength must fall as the frequency rises.
13
RChallenge: a wave of speed 340 m/s has a wavelength of 0.68 m. Find its frequency, in Hz. Write the number.
13.4

Waves transfer energy and information

Year 9
9P6: waves transfer energy and information without transferring matter
Video lesson: Waves transfer energy and informationComing soon
Story. A pupil listens to a radio and a microphone picks up sounds in a music studio. The teacher explains that both waves carry information and energy from one place to another, but the air and the radio waves themselves do not travel all the way with the signal.

Waves transfer energy and, in some cases, information, from one place to another, without transferring matter. The particles of a water wave move up and down about their position. The energy moves on along the water.

Sound waves are used in a microphone to convert pressure changes into electrical signals. Ultrasound waves carry energy used for cleaning and physiotherapy. Radio waves carry information without moving any matter.

Key ideas

  • Waves transfer energy, not matter.
  • Information can be carried by waves, such as radio and sound.
  • A microphone converts sound waves into electrical signals.
  • Ultrasound carries energy, used for cleaning and physiotherapy.
Worked example 13.4.1
A water wave moves across a pond. Does the water travel across the pond with the wave? Write yes or no.

Method. Think about the particles.

  1. Think. The water particles only move up and down about their positions.
    up and down
  2. Decide. So the water does not travel across; the answer is no.
    no
  3. Write the answer.
    no

Check. The wave transfers energy, not matter. ✓

Worked example 13.4.2
What does a microphone convert sound waves into? Write the words.

Method. Recall the purpose of a microphone.

  1. Recall. A microphone changes the pressure of sound into an electrical signal.
    electrical signal
  2. Name it. So it converts sound waves into electrical signals.
    electrical signals
  3. Write the answer.
    electrical signals

Check. The electrical signal carries the information. ✓

Worked example 13.4.3
Which type of wave is used for cleaning and physiotherapy: ultrasound or radio? Write the word.

Method. Recall the use.

  1. Recall. Ultrasound is used for cleaning and physiotherapy.
    cleaning and physiotherapy
  2. Name it. So the wave is ultrasound.
    ultrasound
  3. Write the answer.
    ultrasound

Check. Ultrasound carries energy. ✓

Watch out

Watch out: a radio wave carries information but is not a matter wave. Information is not the same as matter moving.

Exam tip

Exam tip. When asked what a wave transfers, say “energy and, in some cases, information”, and “not matter”.

Try it (with your teacher, or a grown-up at home). With your teacher, flick a rope or stand a row of books and push one at the end. Say whether the rope or books move along with the wave, and what moves on.

Exercise 13D  Waves transfer energy and information

1
FDo waves transfer matter from one place to another? Write yes or no.
2
FWhat do waves transfer from one place to another? Write the word.
3
FWhich type of wave is used to carry information in a radio signal? Write the words.
4
FWhat does a microphone change sound into? Write the words.
5
FWhich wave is used for cleaning and physiotherapy? Write the word.
6
PSIn a water wave, do the water particles move across the pond with the wave? Write yes or no.
7
PSA radio signal carries a song from a station to a radio. What is carried: energy and information, or matter? Write the words.
8
PSA pupil claims that sound moves the air all the way from the speaker to the ear. Is this correct? Write yes or no.
9
PSName one use of a wave that carries energy, other than ultrasound. Accept any one: cooking with microwaves, or heating with infrared.
10
RExplain how a sound wave carries energy from a drum to your ear, without moving the air all the way. Write one sentence. Accept any sentence saying the particles vibrate and pass the vibration on, so the energy moves while the particles stay near their positions.
11
RChallenge: explain why a radio signal can carry information across a distance without any matter moving between the transmitter and the receiver. Accept any sentence saying the information is carried by the energy of the wave, not by moving matter.
13.5

The electromagnetic spectrum

Year 9
9P6: the electromagnetic spectrum in depth: order by wavelength and frequency; uses and hazards explained through energy per photon (basic); all electromagnetic waves travel at the same speed in a vacuum
Video lesson: The electromagnetic spectrumComing soon
Story. A hospital uses one type of wave to see inside a patient, and another type to sterilise equipment. A pupil asks why the two waves are used differently, although they are both part of the same family of waves.

All electromagnetic waves are transverse, and they all travel at the same speed in a vacuum: about 3 x 108 m/s. They differ in wavelength and frequency. In order of increasing wavelength (decreasing frequency): gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves. The shorter the wavelength, the higher the frequency.

Higher frequency waves carry more energy per photon. This explains the hazards: ultraviolet, X-rays and gamma rays can damage cells, while radio waves carry too little energy to do this.

The electromagnetic spectrum (longest wavelength on the left)radiomicrowavesinfraredvisible lightultravioletX-raysgammaincreasing frequency and energy per photon to the right
The electromagnetic spectrum, from radio waves to gamma rays
Wave (longest to shortest wavelength)Typical useHazard
radio wavesbroadcasting and communicationvery little; long wavelength
microwavescooking food and mobile phone signalsheating of body tissue at high power
infraredremote controls and heatersburns from strong heat
visible lightseeing and photographyvery bright light can damage the eye
ultravioletfluorescent lamps and security markingsunburn and skin damage
X-raysmedical imaging and checking materialscan damage cells; limited exposure
gamma raystreating cancer and sterilising equipmentcan damage cells; strictly controlled
Each part of the spectrum, with a typical use and a hazard

Key ideas

  • All electromagnetic waves travel at about 3 x 108 m/s in a vacuum.
  • Order by wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
  • Shorter wavelength means higher frequency and more energy per photon.
  • Ultraviolet, X-rays and gamma rays are hazardous to cells.
Worked example 13.5.1
Which wave has the longest wavelength: infrared or X-rays? Write the word.

Method. Use the order of the spectrum.

  1. Look. Infrared lies at longer wavelengths than X-rays.
    longer wavelengths
  2. Name it. So infrared has the longer wavelength.
    infrared
  3. Write the answer.
    infrared

Check. X-rays have higher frequency and energy. ✓

Worked example 13.5.2
Which part of the spectrum carries the most energy per photon: microwaves or gamma rays? Write the words.

Method. Higher frequency means more energy per photon.

  1. Look. Gamma rays have a much higher frequency than microwaves.
    higher frequency
  2. Name it. So gamma rays carry more energy per photon.
    gamma rays
  3. Write the answer.
    gamma rays

Check. Gamma rays are at the high-frequency end. ✓

Worked example 13.5.3
All electromagnetic waves travel at the same speed in a vacuum. Write the speed in m/s, as 3 x 10 to the power 8. Write the number.

Method. Recall the speed.

  1. Recall. The speed in a vacuum is about 3 x 108 m/s.
    3 x 108
  2. Name it. So the speed is 3 x 108 m/s.
    3 x 10^8
  3. Write the answer.
    3 x 10^8

Check. The same for radio and gamma waves. ✓

Watch out

Watch out: the order of the spectrum is by wavelength, not by how strong a wave is. Radio waves are not weak in every sense; they carry little energy per photon.

Exam tip

Exam tip. Learn the order with a mnemonic. Remember that the shorter the wavelength, the higher the frequency and the energy.

Try it (with your teacher, or a grown-up at home). Using a sunny window (never look at the Sun), and a mobile phone or a TV remote, describe which waves you cannot see but can detect. Use a grown-up to check that your phone is not used near the eyes.

Exercise 13E  The electromagnetic spectrum

1
FWhat is the speed of all electromagnetic waves in a vacuum, to one significant figure? Write the number as 3 x 10 to the power 8.
2
FWhich electromagnetic wave is used for broadcasting? Write the words.
3
FWhich electromagnetic wave is used in medical imaging? Write the words.
4
FWhich part of the spectrum is seen by the human eye? Write the words.
5
FWhich electromagnetic wave causes sunburn? Write the words.
6
PSWhich part of the spectrum has the longest wavelength: infrared, or microwaves? Write the words.
7
PSWhich part of the spectrum has the highest frequency: ultraviolet or infrared? Write the word.
8
PSIn the order of increasing wavelength, which comes immediately before visible light? Write the words.
9
PSIs the speed of radio waves in a vacuum the same as the speed of gamma rays in a vacuum? Write yes or no.
10
RExplain why ultraviolet can damage skin but visible light does not, in terms of energy per photon. Write one sentence. Accept any sentence saying ultraviolet has a higher frequency and more energy per photon, so it can damage cells.
11
RChallenge: explain why radio waves are not hazardous in the same way as gamma rays. Accept any sentence saying radio waves have low frequency and little energy per photon, so they do not damage cells in the same way.

Chapter summary

SkillMethod
Transverse and longitudinalTransverse: vibration at right angles to travel (light, water). Longitudinal: parallel (sound).
Wave termsAmplitude (height from rest); wavelength (crest to crest); frequency (Hz); period (s); T = 1 / f.
Wave equationv = f x lambda; f = v / lambda; lambda = v / f.
Energy and informationWaves transfer energy, and some carry information, without transferring matter.
Electromagnetic spectrumRadio, microwave, infrared, visible, ultraviolet, X-ray, gamma; all travel at 3 x 108 m/s in a vacuum.
HazardsHigher frequency means more energy per photon; ultraviolet, X-rays and gamma rays can damage cells.

Can you…?

  • I can distinguish transverse and longitudinal waves, with examples
  • I can name and measure amplitude, wavelength, frequency and period
  • I can use v = f x lambda and T = 1 / f in simple calculations
  • I can explain how waves transfer energy and information without transferring matter
  • I can order the electromagnetic spectrum, and link each part to a use and a hazard

Key terms

transverse wave
a wave in which the vibration is at right angles to the direction of energy transfer
longitudinal wave
a wave in which the vibration is parallel to the direction of energy transfer
amplitude
the maximum displacement of a wave from its rest position
wavelength
the distance from one point on a wave to the same point on the next wave, such as crest to crest
frequency
the number of waves passing a point each second, measured in hertz
hertz
the unit of frequency: one wave per second
period
the time for one full wave to pass a point, in seconds
compression
a region where the particles of a longitudinal wave are crowded together
rarefaction
a region where the particles of a longitudinal wave are spread out
electromagnetic spectrum
the range of electromagnetic waves, from radio waves to gamma rays
photon
a packet of electromagnetic energy; higher frequency photons carry more energy

Exercise 13Z  Check-up

1
Is sound a transverse or a longitudinal wave? Write the word.
2
What is the name of the maximum displacement from rest of a wave? Write the word.
3
A wave has a frequency of 20 Hz. What is its period, in seconds? Write the number.
4
A wave has a frequency of 50 Hz and a wavelength of 4 m. What is its speed, in m/s? Write the number.
5
A wave travels at 300 m/s with a wavelength of 3 m. What is its frequency, in Hz? Write the number.
6
Which part of the spectrum is used for broadcasting? Write the words.
7
Which part of the spectrum has the shortest wavelength: X-rays or infrared? Write the word.
8
What do waves transfer, other than matter? Write the word.
9
Name the speed of all electromagnetic waves in a vacuum, as 3 x 10 to the power 8. Write the number.
10
Explain why a higher frequency electromagnetic wave carries more energy per photon. Write one sentence. Accept any sentence saying energy per photon increases with frequency.

Total 21 marks. Allow about 21 minutes.

Exercise 13X  Practice test questions

1
FIs light a transverse or a longitudinal wave? Write the word.[1 mark]
2
PSA wave has a period of 0.25 s. What is its frequency, in hertz? Write the number.[1 mark]
3
PSA wave travels at 340 m/s with a frequency of 85 Hz. Find its wavelength, in metres. Write the number.[2 marks]
4
FName the wave used in medical imaging and the wave used for sunburn. Write the two words.[2 marks]
5
FDescribe the difference between a transverse and a longitudinal wave, in one sentence. Accept any sentence saying the vibration is at right angles to the direction of travel in a transverse wave, and parallel in a longitudinal wave.[2 marks]
6
PSA wave has a frequency of 2 Hz and a wavelength of 0.5 m. Find its speed, in m/s. Write the number.[2 marks]
7
FPut these in order of increasing wavelength, starting with the longest: X-rays, radio waves, visible light. Write the three words in order.[2 marks]
8
RExplain how a sound wave transfers energy to your ear without moving the air all the way. Write two sentences. Accept any answer saying the particles vibrate and pass the vibration on, so the energy moves while the particles stay near their places.[3 marks]
9
RExplain why ultraviolet is more hazardous than visible light, in terms of energy per photon. Write two sentences. Accept any answer saying ultraviolet has a higher frequency, so more energy per photon, which can damage cells.[3 marks]
10
PSA ripple tank makes waves of wavelength 4 cm at 5 Hz. Find the speed of the waves, in cm/s, and give the period, in seconds. Write the two numbers.[3 marks]
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