OCR GCSE Physics A: Electromagnetic waves and the spectrum (J249) – 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 statements P5.2a to P5.2f of topic P5.2, The electromagnetic spectrum, in the OCR GCSE (9-1) Gateway Science Physics A (J249) specification, Version 5.0 (July 2026). All of them are suitable for both Foundation and Higher Tier. Where a question gives no value for the speed of electromagnetic waves, use 3.0 × 10⁸ m/s in a vacuum. Read the study guide and revision notes first if you need to. Course pages: OCR GCSE Physics hub and the checklist.

Questions

1. The seven groups of the electromagnetic spectrum are: radio, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays.

(a) List them in order of increasing wavelength, starting with the shortest. [2] (b) State which group has the highest frequency. [1]

2. Electromagnetic waves are transverse.

(a) State what is meant by a transverse wave. [1] (b) Sound waves cannot travel through a vacuum but light can. Explain why. [2]

3. A beam of light has frequency 5.0 × 10¹⁴ Hz. Calculate its wavelength in nanometres. [3]

4. A radio station transmits at 909 kHz. Calculate the wavelength of the waves. [3]

5. A bowl of soup is placed in a microwave oven and warms up. Explain how energy is transferred to the soup. Name the source and the absorber. [4]

6. A probe is 7.8 × 10¹¹ m from Earth. A radio message is sent to it.

(a) Calculate the time taken for the message to reach the probe, in seconds. [2] (b) Give your answer to part (a) in minutes. [1] (c) A second message is sent using microwaves at the same moment. Say whether it arrives earlier, later or at the same time. [1]

7. Green light has a wavelength of 530 nm.

(a) State the range of the electromagnetic spectrum that the human eye can detect. [1] (b) Calculate the frequency of the green light. [2] (c) A hot grill element, switched on only briefly, gives out infrared but no visible light. Explain why you cannot see this infrared. [2]

8. State whether each statement is true or false.

(a) Light waves are longitudinal. [1] (b) Light can travel through the empty space between the Sun and Earth. [1] (c) Light travels more slowly than radio waves in a vacuum. [1] (d) Violet light has a higher frequency than red light. [1]

9. A student removes the turntable from a microwave oven and heats a flat slab of processed cheese. Melted spots appear. The student measures the distance between the first and the seventh melted spots as 33.0 cm.

(a) Calculate the distance between neighbouring spots. [1] (b) The distance between neighbouring spots is half the wavelength. Calculate the wavelength. [1] (c) Calculate the frequency of the microwaves. [3] (d) Explain why measuring across six gaps is better than measuring one gap. [1]

10. Wave R is a radio wave of frequency 1.5 × 10⁸ Hz. Wave X is an X-ray of frequency 3.0 × 10¹⁸ Hz. Both travel in a vacuum.

(a) Calculate the wavelength of each wave. [4] (b) Calculate how many times greater the frequency of wave X is than that of wave R. [1] (c) State how the wavelength of wave X compares with that of wave R, and the speed of wave X compared with the speed of wave R. [1]

11. The table shows three electromagnetic waves in a vacuum. Each has one value missing.

Wave	Wavelength	Frequency
A	1.5 cm
B		7.0 × 10¹⁴ Hz
C	2.0 × 10⁻⁵ m

(a) Calculate the missing values. Give each answer in standard form. [6] (b) Name the group of the spectrum to which each wave belongs. [3]

Answers

1. (a) Gamma rays, X-rays, ultraviolet, visible light, infrared, microwave, radio. Gamma rays, X-rays and ultraviolet correctly placed first [1]; the complete order is correct [1]. [2] (b) Gamma rays. [1] [1] Examiner insight: the direction in the question matters. Answers that give the list in the right order but from longest wavelength first usually lose the credit, so reread “starting with the shortest” before writing.

2. (a) The oscillations are at right angles to the direction of travel of the wave. [1] [1] (b) Sound needs particles to vibrate and pass the wave on, and a vacuum has no particles. [1] Light is an electromagnetic wave made of oscillating electric and magnetic fields, so it needs no material medium. [1] [2] Examiner insight: an answer that only says “sound needs air” is incomplete. Linking to what the wave is made of, particles or fields, is what separates the two marks.

3. λ = v / f [1]; λ = 3.0 × 10⁸ / 5.0 × 10¹⁴ = 6.0 × 10⁻⁷ m [1]; 600 nm [1] [3] Examiner insight: working in metres first and then converting to nanometres at the end is safer than converting at the start. A final answer in metres with no conversion does not answer “in nanometres”.

4. f = 909 kHz = 9.09 × 10⁵ Hz [1]; λ = 3.0 × 10⁸ / 9.09 × 10⁵ [1]; 330 m [1] [3] Examiner insight: the kilo prefix is where most slips happen. Check that the size fits the group: radio wavelengths are metres to kilometres, so 0.33 m or 330 000 m would be suspect.

5. The source is the microwave emitter in the oven. [1] The microwaves transfer energy to the soup by travelling through the air to it. [1] The absorber is the soup, in particular the water in it, which takes in the energy. [1] This increases the energy of the soup, so its temperature rises. [1] [4] Examiner insight: four marks need four distinct ideas: source, transfer by the wave, absorber, effect on the absorber. Saying only “the microwaves heat the soup” covers little of that.

6. (a) time = distance / speed [1]; 7.8 × 10¹¹ / 3.0 × 10⁸ = 2600 s (2.6 × 10³ s) [1] [2] (b) 2600 / 60 = 43 minutes (43.3) [1] [1] (c) The same time, because all electromagnetic waves travel at the same speed in a vacuum. [1] [1] Examiner insight: give the unit that the question asks for at each stage. A part (b) answer of 43 with no unit, or 2600 minutes, usually does not earn the mark.

7. (a) Only a narrow range, about 400 nm to 700 nm, the visible light region. [1] [1] (b) 530 nm = 5.3 × 10⁻⁷ m, f = 3.0 × 10⁸ / 5.3 × 10⁻⁷ [1]; 5.7 × 10¹⁴ Hz [1] [2] (c) Infrared has a longer wavelength than visible light, outside the range the eye can detect. [1] The eye does not respond to it, so it gives no sensation of sight, although the energy is still carried. [1] [2] Examiner insight: in part (c), say that the limit is in the detector, the eye. Statements such as “infrared is not light” or “it is too weak” miss the point being tested.

8. (a) False. [1] (b) True. [1] (c) False. [1] (d) True. [1] [4] Examiner insight: in true or false questions, do not guess at (c) from the idea that “light is fast”. All electromagnetic waves share one speed in a vacuum.

9. (a) Six gaps, 33.0 / 6 = 5.5 cm [1] [1] (b) 2 × 5.5 = 11.0 cm (0.110 m) [1] [1] (c) f = v / λ [1]; 3.0 × 10⁸ / 0.110 [1]; 2.7 × 10⁹ Hz (2.7 GHz) [1] [3] (d) Any reading error is shared out between six gaps, so the error in one gap is smaller. [1] [1] Examiner insight: part (c) needs the wavelength in metres. Using 11.0 with the speed in m/s gives a frequency 100 times too big, and a check against the microwave group would show it.

10. (a) Wave R: λ = v / f = 3.0 × 10⁸ / 1.5 × 10⁸ [1]; 2.0 m [1]. Wave X: λ = 3.0 × 10⁸ / 3.0 × 10¹⁸ [1]; 1.0 × 10⁻¹⁰ m [1] [4] (b) 3.0 × 10¹⁸ / 1.5 × 10⁸ = 2.0 × 10¹⁰ times [1] [1] (c) The X-ray wavelength is 2.0 × 10¹⁰ times shorter, and the speed is the same. [1] [1] Examiner insight: the “how many times” in part (b) is a ratio with no unit. The same factor appears in the wavelengths, which gives you a way to check part (a).

11. (a) A: f = 3.0 × 10⁸ / 1.5 × 10⁻² [1]; 2.0 × 10¹⁰ Hz [1]. B: λ = 3.0 × 10⁸ / 7.0 × 10¹⁴ [1]; 4.3 × 10⁻⁷ m [1]. C: f = 3.0 × 10⁸ / 2.0 × 10⁻⁵ [1]; 1.5 × 10¹³ Hz [1] [6] (b) A is microwave [1]. B is visible light [1]. C is infrared [1]. [3] Examiner insight: the table has a centimetre in one cell. Converting 1.5 cm to 1.5 × 10⁻² m before substituting is what prevents a factor of 100 error. Use the group sizes to sense-check each answer.

Where marks are usually lost

• Listing the spectrum in the wrong direction because the question starts at the other end.
• Saying EM waves need a medium, or giving sound as an example.
• Not converting kHz, MHz, GHz, cm, μm or nm before substituting.
• Writing a power of ten that puts the answer in the wrong group.
• Claiming that one group travels faster than another in a vacuum.
• Explaining energy transfer without naming the absorber or its change.
• Giving the spacing of melted spots as the wavelength without doubling it.
• Treating the eye’s limit as a property of infrared or ultraviolet instead of the detector.

Next steps

• Re-read the revision notes and the study guide.
• Course pages: OCR GCSE Physics hub and the checklist.
• Try the free 10-minute diagnostics to find what to revise next.
• Book a free trial class.

Official syllabus

OCR GCSE (9-1) Gateway Science Physics A (J249), Version 5.0 (July 2026), first assessment 2018, published by OCR. Topic P5.2, statements P5.2a to P5.2f.