AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2018: Question 5

8 marks · Standard Demand difficulty · Short Answer

Explain the difference between transverse and longitudinal waves, calculate the wavelength of radio waves from their frequency and wave speed, and describe how radio waves induce signals in a car radio aerial circuit.

Practise this question

Question

The question page shows three linked parts about waves and radio transmission. Part 05.1 states that a car aerial receives radio waves from a radio transmitter, that radio waves are transverse and sound waves are longitudinal, then asks for the difference between transverse and longitudinal waves for 2 marks. Part 05.2 gives a radio-wave frequency of 4.8 × 10^9 hertz and the speed of electromagnetic waves as 3.0 × 10^8 metres per second, then asks the student to calculate the wavelength to 2 significant figures for 3 marks, with answer lines and a final blank labelled 'Wavelength = ... m'. Part 05.3 asks for 3 marks to describe how radio waves reaching the car aerial produce signals in the electrical circuit of the car radio, with several lined spaces for a written response.
Question text

05 A car aerial receives radio waves from a radio transmitter.

Radio waves are transverse waves.

Sound waves are longitudinal waves.

05.1 Describe the difference between transverse waves and longitudinal waves.

[2 marks]

The radio waves have a frequency of 4.8 × 109 Hz

05.2

Wave speed of electromagnetic waves = 3.0 × 108 m/s

Calculate the wavelength of the radio waves.

Give your answer to 2 significant figures.

[3 marks]

16 Wavelength = m

05.3 Describe how the radio waves reaching the car aerial produce signals in the electrical

circuit of the car radio.

[3 marks]

Mark scheme

Show the mark scheme The mark scheme is a table for question 05 with rows for 05.1, 05.2 and 05.3, totaling 8 marks. For 05.1, it awards marks for stating that longitudinal-wave oscillations are parallel to the direction of energy transfer and transverse-wave oscillations are perpendicular, with allowances for equivalent descriptions such as peaks and troughs versus compressions and rarefactions. For 05.2, it shows the equation 3.0 × 10^8 = 4.8 × 10^9 × lambda, giving lambda = 0.0625 m and the accepted rounded answer 0.063 m or 6.3 × 10^-2 m, with marks for rearranging, calculating, and correct significant figures. For 05.3, it credits any three points from: the aerial absorbs radio waves or energy, electrons in the aerial vibrate, an alternating current is created in the aerial circuit, and the signal frequency is the same as the radio wave.

AO /

Question Answers Extra information Mark

Spec. Ref.

05.1 in a longitudinal wave, the 1 AO1

oscillations / vibrations are 6.6.1.1

parallel to the direction of allow direction of travel for

energy transfer energy transfer

in a transverse wave, the 1

oscillations / vibrations are

perpendicular to the direction of allow direction of travel for

energy transfer energy transfer

if no other mark scored allow 1

mark for (oscillations / vibrations

of) longitudinal waves are

parallel and (oscillations /

vibrations of ) transverse waves

are perpendicular

if no other mark scored allow 1

mark for transverse waves have

peaks and troughs and

longitudinal waves have

compressions and rarefactions

05.2 an answer of 0.063 (m) scores 3 AO2

marks 6.6.1.2

89 3.0 × 108

3.0 × 10 = 4.8 × 10 × λ allow λ = 1

4.8 × 109

this mark may be awarded if the

standard form values are

incorrectly converted

λ = 0.0625 (m) 1

λ = 0.063 (m) allow an answer to 2 sig figs that 1

or is consistent with their

λ = 6.3 × 10-2 (m) calculated value of λ and has

required rounding

AO /

Spec. Ref.

05.3 any three from: 3 AO1

6.6.2.3

• (the car aerial) absorbs

radio waves or energy

• electrons are made to

vibrate (in the aerial)

• creating an alternating

current (in the aerial

circuit)

• the (signal) frequency is

the same (as the radio

wave)

Total 8

How to answer it

Radio Waves, Wave Types and Aerials

AQA GCSE Combined Science: Trilogy • Question 05

What this question tests

This question checks whether you can describe wave properties, use the wave equation correctly, and explain how a radio aerial detects electromagnetic waves and turns them into an electrical signal. Full marks come from clear key words, correct units, and a step-by-step calculation.

Part 05.1 — Difference between transverse and longitudinal waves [2 marks]

✅ Correct answer

In a longitudinal wave, the vibrations/oscillations are parallel to the direction of travel.
In a transverse wave, the vibrations/oscillations are perpendicular to the direction of travel.

💡 Key knowledge

  • Parallel means “in the same direction”.
  • Perpendicular means “at 90° to”.
  • For extra support in revision: transverse waves have peaks and troughs; longitudinal waves have compressions and rarefactions.

🧠 Exam technique

  • Use the words vibrations or oscillations and link them to the direction of travel.
  • This is a 2-mark “describe” question: one clear statement for each wave type usually earns both marks.

❌ Common errors

  • Saying only “one is up and down, one is along” without linking to direction of travel.
  • Confusing perpendicular with parallel.
  • Writing about wavelength or frequency instead of the wave direction.
How marks are awarded: 1 mark for describing longitudinal waves correctly, 1 mark for describing transverse waves correctly.

Part 05.2 — Calculate the wavelength [3 marks]

📐 Calculation: step by step

  1. Use the wave equation: wave speed = frequency × wavelength
  2. Substitute the values: 3.0 × 10⁸ = 4.8 × 10⁹ × λ
  3. Rearrange: λ = 3.0 × 10⁸ ÷ 4.8 × 10⁹
  4. Calculate: λ = 0.0625 m
  5. Round to 2 significant figures: λ = 0.063 m

✅ Correct answer

Wavelength = 0.063 m
or 6.3 × 10⁻² m

💡 Key knowledge

  • Wave equation: wave speed = frequency × wavelength
  • So wavelength = wave speed ÷ frequency
  • Units matter: speed in m/s, frequency in Hz, wavelength in m

🧠 Exam technique

  • Write the equation first to secure the method mark.
  • Keep the numbers in standard form if you can.
  • Finish with the correct rounding: the question asks for 2 significant figures.

❌ Common errors

  • Using frequency ÷ speed instead of speed ÷ frequency.
  • Forgetting to give the answer in metres.
  • Not rounding correctly to 2 significant figures.
  • Writing 0.0625 as the final answer when the question asks for rounding.
How marks are awarded: 1 mark for correct substitution into the wave equation, 1 mark for correct rearrangement/calculation, 1 mark for a final answer of 0.063 m (or equivalent to 2 s.f.).

Part 05.3 — How radio waves produce signals in a car radio circuit [3 marks]

✅ Correct answer

Any three of the following:

  • The car aerial absorbs the radio waves / energy.
  • Electrons are made to vibrate in the aerial.
  • This creates an alternating current in the aerial circuit.
  • The signal frequency is the same as the radio wave frequency.

💡 Key knowledge

  • An aerial is a receiver of electromagnetic waves.
  • The incoming wave transfers energy to the electrons in the metal.
  • The electrical signal produced is an AC signal matching the radio wave’s frequency.

🧠 Exam technique

  • This is a “describe” question: give linked steps, not just single words.
  • Best answers usually follow the sequence:
    absorbed → electrons vibrate → alternating current → same frequency
  • You only need three valid points for full marks.

❌ Common errors

  • Saying the aerial “makes sound” — this is not what the mark scheme wants.
  • Confusing the radio wave frequency with the volume or loudness.
  • Writing only “the aerial picks up the signal” without explaining how.

📐 What to draw if asked for a diagram

If you needed to show the idea in a sketch, draw:

  • A radio wave arriving at a car aerial.
  • Arrows showing energy transfer to the aerial.
  • Electrons moving back and forth in the aerial wire.
  • A labelled alternating current in the circuit.
How marks are awarded: Any three correct statements from the mark scheme earn the 3 marks. Top answers are clear, ordered, and use the correct physics vocabulary.

Quick exam recap

⭐ Facts to remember

  • Transverse = vibrations perpendicular to travel.
  • Longitudinal = vibrations parallel to travel.
  • Wave equation: v = f × λ
  • Aerials induce alternating current.

⭐ Best way to gain marks

  • Use key words exactly.
  • Show the calculation clearly.
  • Check units and rounding.
  • For explanation questions, give a chain of linked ideas.

Topics

Physics · P6: Waves · P2: Electricity

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Higher), 2018. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.