OCR A Level Physics A: Wave motion, polarisation and wave effects (H556) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover section 4.4.1 Wave motion, statements (a) to (g), of the OCR A Level Physics A (H556) specification, Version 3.0 (March 2026), for first assessment in 2017. This is full A level content. Learn the content from the study guide or the revision notes. The course hub, the printable checklist and the free 10-minute diagnostics help you plan.

Use v = 343 m s⁻¹ for the speed of sound in air.

Questions

1. Compare how particles move in transverse and in longitudinal waves relative to the energy flow. Name one example of each. [3]

2. A signal generator is connected to an oscilloscope. One complete cycle of the trace spans 2.4 divisions and the time base is set to 20 μs per division. Calculate the frequency of the signal. [3]

3. A wave travels along a rope at 12 m s⁻¹ with a frequency of 8.0 Hz. (a) Calculate the wavelength. [2] (b) Two points on the rope are 0.45 m apart along the wave. Calculate the phase difference between them in degrees. [2]

4. A longitudinal wave travels to the right. The table shows the displacement of particles at one instant, with displacement to the right taken as positive.

Position x / cm	0	1	2	3	4	5	6	7	8
Displacement / mm	0	1.4	2.0	1.4	0	-1.4	-2.0	-1.4	0

(a) State the wavelength. [1] (b) State the position of the centre of a compression, and explain your choice. [2] (c) Explain why a graph of this data should not be described as showing the shape of the wave. [1]

5. Describe how a ripple tank can be used to measure the wavelength of water waves from a vibrating dipper, and how the speed of the waves is then found. [4]

6. A dipper vibrates at 14 Hz. When the pattern is frozen, five wavelengths span 85 mm in the deep region of a tank. (a) Calculate the wavelength. [1] (b) Calculate the speed of the waves. [1] (c) The waves cross into a shallow region where their speed is 0.168 m s⁻¹. Calculate the new wavelength and state what happens to the frequency. [3] (d) Explain why the wavefronts change direction if they meet the boundary at an angle. [1]

7. Sound of frequency 2.0 kHz passes through a doorway 0.90 m wide. Light of wavelength 5.0 × 10⁻⁷ m also passes through it. Explain why a listener out of line of sight can hear the sound, but cannot see the lamp. [4]

8. A microwave transmitter and a receiver are placed facing each other, and the receiver is connected to a meter. (a) Describe what happens to the meter reading as the receiver is rotated slowly through 90° about the line joining the two. [2] (b) A metal grille is then placed between them. Describe how the reading changes as the grille is rotated through 90°, and state what this shows about the microwaves. [3]

9. A driver looks at the surface of a wet road through a Polaroid filter and rotates the filter slowly through 360°. The brightness of the glare reaches a minimum twice. Explain this observation, and say what it shows about the reflected light. State why sound would not behave in this way. [4]

10. A small loudspeaker emits sound with a total power of 0.50 W equally in all directions. (a) Calculate the intensity at a distance of 3.0 m. [2] (b) The eardrum has an area of 5.0 × 10⁻⁵ m². Calculate the power entering the ear at this distance. [2] (c) Calculate the distance at which the intensity falls to one quarter of its value at 3.0 m. [1]

11. A laser emits a beam of power 4.0 mW. The beam has a circular cross-section of diameter 2.0 mm. (a) Calculate the intensity of the beam. [2] (b) A lens spreads the beam to a diameter of 4.0 mm with no loss of power. Calculate the new intensity, and state the factor by which the amplitude of the wave changes. [3]

12. A student investigates a source of ultrasound and a detector that gives a signal amplitude. The student measures the amplitude A of the detector signal and the intensity I of the wave at the detector.

A / mV	1.0	2.0	3.0	4.0
I / μW m⁻²	2.5	10.0	22.5	40.0

(a) Calculate I/A² for each reading. [2] (b) Describe the relationship that the ratios reveal between I and A. [1] (c) Predict the intensity when A = 5.0 mV. [1] (d) State which graph of the data would give a straight line through the origin, and what its gradient would represent. [2] (e) The detector is moved to twice the distance from a small source that radiates equally in all directions. The amplitude was 4.0 mV. State the new amplitude, with a reason. [2]

Answers

1. Transverse: particles oscillate perpendicular to the energy flow [1]. Longitudinal: they oscillate along the energy flow [1]. Examples: a wave on a rope, light or ripples (transverse); sound in air (longitudinal) [1]. [3] Examiner insight: State both directions relative to the energy flow.

2. T = divisions × time base = 2.4 × 20 × 10⁻⁶ [1] = 4.8 × 10⁻⁵ s. f = 1/T = 1/(4.8 × 10⁻⁵) [1] = 2.1 × 10⁴ Hz (20.8 kHz) [1]. [3] Examiner insight: Using the time base value as the period without multiplying by the number of divisions is a common slip, and answers in hertz need the conversion from microseconds done correctly.

3. (a) λ = v/f = 12/8.0 [1] = 1.5 m [1]. (b) 0.45/1.5 = 0.30 of a cycle [1]; 0.30 × 360 = 108° [1]. [4] Examiner insight: Show the fraction of a cycle before converting to degrees, and give the unit of the angle.

4. (a) 8 cm [1]. (b) At x = 4 cm [1]. Particles on its left (at 3 cm) are displaced right and particles on its right (at 5 cm) are displaced left, so they are pushed together [1]. (c) The graph plots displacement along the direction of travel, so the particles do not move up and down; a longitudinal wave has no crests, only compressions and rarefactions [1]. [4] Examiner insight: Naming the position is not enough: describe how neighbouring particles move towards each other.

5. Use a vibrating dipper at a known frequency and a lamp above the tank to project the pattern onto a screen [1]. Use a stroboscope matched to the dipper frequency so the pattern appears stationary [1]. Measure the distance across several wavelengths with a ruler and divide by the number of wavelengths, correcting for any magnification [1]. Then v = fλ using the frequency of the dipper [1]. [4] Examiner insight: Measuring across several wavelengths reduces the percentage uncertainty, so say so.

6. (a) λ = 85/5 = 17 mm [1]. (b) v = fλ = 14 × 0.017 = 0.24 m s⁻¹ (0.238) [1]. (c) λ = v/f = 0.168/14 [1] = 0.012 m (12 mm) [1]. The frequency stays at 14 Hz [1]. (d) One side of each wavefront slows before the other, so the wavefront turns [1]. [6] Examiner insight: “The frequency stays the same” must be stated, since the source fixes it; a changed wavelength alone is only half of the point.

7. λ = v/f = 343/2000 = 0.17 m [1]. This is comparable to the 0.90 m doorway [1], so the sound diffracts and spreads out into the room beyond [1]. Light has a wavelength far smaller than the doorway, so it does not spread and cannot be seen round the corner [1]. [4] Examiner insight: Compare the wavelength with the gap for both waves, and say the light’s diffraction is negligible.

8. (a) The reading falls [1] to a minimum close to zero after 90° [1]. (b) The reading changes between a larger and a smaller value as the grille is rotated, with the signal stronger when the rods are at right angles to the oscillations of the wave [1]. This shows the microwaves are plane polarised [1], so they are a transverse wave [1]. [5] Examiner insight: Say what the observation proves. A description of the meter alone does not answer “state what this shows”.

9. The reflected light is partly polarised [1]. A Polaroid filter transmits only one plane of oscillation, so the glare is dimmest when the filter’s transmission direction is perpendicular to the glare’s plane of oscillation [1]. This happens twice in a full turn, once for each such position 180° apart [1]. Sound would not show this because it is longitudinal, with oscillations along its direction of travel, so it cannot be polarised [1]. [4] Examiner insight: Link the minimum to the relative orientation of filter and light. A statement that the light is polarised without this link gains less credit.

10. (a) I = P/(4πr²) = 0.50/(4π × 3.0²) [1] = 4.4 × 10⁻³ W m⁻² [1]. (b) Power = I × A = 4.42 × 10⁻³ × 5.0 × 10⁻⁵ [1] = 2.2 × 10⁻⁷ W [1]. (c) Intensity ∝ 1/r², so quarter intensity needs twice the distance: 6.0 m [1]. [5] Examiner insight: Carry the unrounded intensity into part (b) and give units on every answer.

11. (a) Area = π(1.0 × 10⁻³)² = 3.14 × 10⁻⁶ m² [1]. I = P/A = 4.0 × 10⁻³ / 3.14 × 10⁻⁶ = 1.3 × 10³ W m⁻² [1]. (b) Diameter doubled so area is four times larger, giving I = 3.2 × 10² W m⁻² (318) [1]. Intensity ∝ amplitude², so the amplitude falls to half [1] since the square root of 1/4 is 1/2 [1]. [5] Examiner insight: The radius, not the diameter, goes into πr². Statements about amplitude need the square relationship, not a direct proportion.

12. (a) 2.5, 2.5, 2.5, 2.5 (μW m⁻² per mV²) [2]. (b) I/A² is constant, so I is proportional to A² [1]. (c) 2.5 × 5.0² = 62.5 μW m⁻² [1]. (d) A graph of I against A² [1]. Its gradient is the constant of proportionality, 2.5 μW m⁻² mV⁻² [1]. (e) Intensity falls to one quarter at twice the distance, so amplitude halves to 2.0 mV [1], since intensity ∝ amplitude² [1]. [8] Examiner insight: In data questions, show the calculated ratios for every reading; a conclusion from only one or two rows is weaker.

Where marks are usually lost

• Using the time base setting as the period without multiplying by the divisions per cycle.
• Mixing up the displacement-time and displacement-distance graphs, or calling a longitudinal graph peak a compression.
• Saying the frequency changes in refraction.
• Not comparing the wavelength with the gap width in diffraction answers.
• Describing polarisation observations without concluding that the wave is transverse.
• Treating intensity as proportional to amplitude instead of amplitude squared.
• Putting the diameter instead of the radius into the area of a circle.
• Rounding too early, or omitting units.

Next steps

• Review the revision notes and the study guide.
• Tick off outcomes on the printable checklist and browse the course hub.
• Take the free 10-minute diagnostics to check other topics.
• Book a free trial class.

Official syllabus

OCR A Level in Physics A (H556) specification, Version 3.0 (March 2026), first assessment 2017, published by OCR: section 4.4.1 Wave motion, statements (a) to (g).