CIE A Level Physics
CIE A Level Physics Waves Exam Questions
Free CIE A Level Physics exam questions for Waves, with a mark scheme for every pack. Covers progressive waves, wave equation, intensity, the Doppler effect for sound, electromagnetic spectrum and polarisation including Malus's law.
Waves exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About CIE A Level Physics Waves
Waves is Topic 7 of the Cambridge International AS & A Level Physics (9702) syllabus. It describes progressive waves using displacement, amplitude, phase difference, period, frequency, wavelength and speed, and compares transverse and longitudinal waves. You also study the Doppler effect for sound, the electromagnetic spectrum and polarisation. The topic leads directly into Superposition. Examiners frequently ask you to read wave data from an oscilloscope trace, apply v = fλ, use the Doppler equation for a moving source and calculate transmitted intensity with Malus's law.
What you need to know
- Wave terms Know displacement, amplitude, phase difference, period, frequency, wavelength and speed. Derive and use v = fλ, with f = 1/T.
- Transverse and longitudinal Transverse waves oscillate perpendicular to the direction of energy transfer; longitudinal waves oscillate parallel to it, forming compressions and rarefactions.
- Intensity Intensity is power per unit area and is proportional to amplitude squared, I ∝ A^2.
- Doppler effect For a source moving relative to a stationary observer, observed frequency fo = fs v/(v ± vs), using minus when the source approaches and plus when it recedes.
- Electromagnetic spectrum All electromagnetic waves travel at 3.00 × 10^8 m s^-1 in free space. Know approximate wavelength ranges from radio waves to gamma rays; visible light is about 400 nm to 700 nm.
- Polarisation Only transverse waves can be polarised. Malus's law gives transmitted intensity I = I0 cos^2 θ.
Common mistakes in Waves
- Reading the wavelength from a displacement-time graph. Wavelength comes from a displacement-distance graph; a displacement-time graph gives the period.
- Using the wrong sign in the Doppler equation. An approaching source gives a higher observed frequency, so the denominator must be smaller.
- Thinking intensity is proportional to amplitude. It is proportional to amplitude squared.
- Using cos θ rather than cos^2 θ in Malus's law.
- Saying sound can be polarised. Sound in air is longitudinal and cannot be polarised.
Try three Waves exam-style questions
1. A wave has frequency 50 Hz and wavelength 0.40 m. Calculate its speed. (1 mark)
Show the mark scheme answer
v = fλ = 50 × 0.40 = 20 m s^-1.
2. A source emitting sound of frequency 600 Hz moves directly towards a stationary observer at 30 m s^-1. The speed of sound is 340 m s^-1. Calculate the frequency heard. (2 marks)
Show the mark scheme answer
fo = fs v/(v - vs) = 600 × 340/(340 - 30); fo = 658 Hz.
3. Unpolarised light passes through two polarising filters whose axes are at 60° to each other. The intensity after the first filter is I0. Calculate the intensity after the second filter in terms of I0. (2 marks)
Show the mark scheme answer
I = I0 cos^2 60°; I = 0.25 I0.
Waves FAQs
What does Cambridge AS & A Level Physics Waves cover?
It covers progressive waves and their properties, the wave equation, intensity, transverse and longitudinal waves, the Doppler effect for sound, the electromagnetic spectrum and polarisation.
Which papers is the Waves topic examined in?
It is an AS Level topic assessed in Paper 1 and Paper 2, and using an oscilloscope to measure frequency is a practical skill.
What equations do I need for Waves?
Learn v = fλ, f = 1/T, I ∝ A^2, the Doppler equation fo = fs v/(v ± vs) and Malus's law I = I0 cos^2 θ.
