CCEA A Level Physics
CCEA A Level Physics 2.1 Waves Exam Questions
Free CCEA A Level Physics revision for 2.1 Waves: what you need to know, common mistakes and exam-style questions with answers. Covers transverse and longitudinal waves, polarisation, wave graphs, amplitude, period, frequency, wavelength, phase, v = fλ and the electromagnetic spectrum.
Practise 2.1 Waves with past papers
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About CCEA A Level Physics 2.1 Waves
Waves opens Unit AS 2: Waves, Photons and Astronomy and supplies the vocabulary for refraction, interference, quantum physics and astronomy later in the unit. You need to compare transverse and longitudinal waves, explain polarisation as evidence that a wave is transverse, and read amplitude, period, wavelength and phase from displacement-distance and displacement-time graphs. You must use f = 1/T and v = fλ, and know the order and typical wavelengths of the electromagnetic spectrum. Examiners often ask you to tell the two graph types apart, calculate phase difference and explain why sound cannot be polarised.
What you need to know
- Transverse and longitudinal In a transverse wave the oscillations are perpendicular to the direction of energy transfer (light, water ripples, waves on a string). In a longitudinal wave they are parallel, with compressions and rarefactions (sound).
- Polarisation A polarised transverse wave oscillates in one plane only. Only transverse waves can be polarised, so polarisation shows light is transverse. Examples include Polaroid filters and polarised sunglasses reducing glare.
- Wave graphs A displacement-distance graph shows wavelength and amplitude. A displacement-time graph for one point shows period and amplitude. Make sure you read the axis label before taking a value.
- Wave equations f = 1/T and v = fλ. Frequency is set by the source and stays the same when a wave changes medium; speed and wavelength can change.
- Phase Phase difference compares points in the cycle, given in degrees or radians. Points one wavelength apart are in phase (360° or 2π); points half a wavelength apart are in antiphase (180° or π).
- Electromagnetic spectrum In order of decreasing wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Visible light is about 400 nm (violet) to 700 nm (red); all travel at 3.0 x 10^8 m s-1 in a vacuum.
Common mistakes in 2.1 Waves
- Reading the period from a displacement-distance graph; check whether the horizontal axis is distance or time.
- Saying sound can be polarised; it is longitudinal so it cannot.
- Claiming frequency changes when light enters glass; frequency is constant, speed and wavelength decrease.
- Measuring amplitude from peak to trough; amplitude is from the equilibrium position to a peak.
- Writing typical wavelengths with the wrong order of magnitude, such as X-rays at 10^-6 m; X-rays are around 10^-10 m.
Try three 2.1 Waves exam-style questions
1. A sound wave has frequency 250 Hz and wavelength 1.36 m. Calculate its speed and period. (2 marks)
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v = fλ = 250 x 1.36 = 340 m s-1; T = 1/f = 1/250 = 4.0 x 10^-3 s.
2. Two points on a progressive wave are 0.25 wavelengths apart. State the phase difference in radians. (1 mark)
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π/2 rad (90°).
3. Describe how polarisation shows that light is a transverse wave. (3 marks)
Show the mark scheme answer
Look at a light source through a Polaroid filter and rotate a second filter (analyser); intensity changes from maximum to minimum every 90°; this happens because only transverse waves have oscillations that can be restricted to one plane; longitudinal waves would show no change.
2.1 Waves FAQs
What does CCEA A Level Physics 2.1 Waves cover?
Transverse and longitudinal waves, polarisation, wave graphs and the terms amplitude, period, frequency, wavelength and phase, the wave equation and the electromagnetic spectrum.
Which unit is 2.1 examined in?
It is in Unit AS 2: Waves, Photons and Astronomy.
Which wavelengths of the electromagnetic spectrum should I learn?
Learn the order and an order of magnitude for each region, for example radio above about 1 m, microwaves around 10^-2 m, infrared around 10^-5 m, visible 400 to 700 nm, ultraviolet around 10^-8 m and X-rays around 10^-10 m.
