Question 1 Hard
Higher tier. A mobile phone signal has a frequency of 6.0 × 10⁸ Hz. Electromagnetic waves travel at 3.0 × 10⁸ m/s. Calculate the wavelength.
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Answer: 0.5 m
- wavelength = speed ÷ frequency.
- (3.0 × 10⁸) ÷ (6.0 × 10⁸) = 0.5 m.
The electromagnetic spectrum: GCSE Combined Science Physics practice questions
A second set of questions on the electromagnetic spectrum. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
More questions
Question 2 Hard
Higher tier. Red light has a wavelength of 7.0 × 10⁻⁷ m. Electromagnetic waves travel at 3.0 × 10⁸ m/s. Calculate the frequency.
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Answer: 4.3 × 10¹⁴ Hz
- frequency = speed ÷ wavelength.
- (3.0 × 10⁸) ÷ (7.0 × 10⁻⁷) = 4.3 × 10¹⁴ Hz.
Question 3 Hard
Higher tier. Gamma rays from a source have a wavelength of 2.0 × 10⁻¹² m. Electromagnetic waves travel at 3.0 × 10⁸ m/s. Calculate the frequency of the gamma rays.
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Answer: 1.5 × 10²⁰ Hz
- frequency = speed ÷ wavelength.
- (3.0 × 10⁸) ÷ (2.0 × 10⁻¹²) = 1.5 × 10²⁰ Hz.
Question 4 Hard
Higher tier. Explain how a radio transmitter produces radio waves and how a receiving aerial detects them.
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Answer: An alternating current in the transmitter makes radio waves, and when the waves are absorbed by the receiving aerial they produce an alternating current of the same frequency
- Radio waves are produced by oscillations in an electrical circuit.
- An alternating current in the transmitter aerial makes the waves, and absorbed waves make an alternating current in the receiver.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is the order of the electromagnetic spectrum from longest to shortest wavelength?
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Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.
Check 2
What do all electromagnetic waves have in common?
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They are transverse waves that travel at the same speed in a vacuum.
Check 3
What is the speed of electromagnetic waves in a vacuum?
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About 3.0 × 10⁸ m/s.
Check 4
Which group has the highest frequency?
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Gamma rays.
Check 5
Which group has the longest wavelength?
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Radio waves.
Check 6
What happens to wavelength and frequency from radio waves to gamma rays?
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The wavelength decreases and the frequency increases.
Check 7
What is the wave equation?
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Wave speed = frequency × wavelength.
Check 8
Why can electromagnetic waves travel through a vacuum?
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They are oscillations of electric and magnetic fields, so they do not need a substance to travel through.
Check 9
Give a use of radio waves.
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Television and radio broadcasts.
Check 10
Give two uses of microwaves.
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Satellite communication and cooking.
Check 11
Give two uses of infrared.
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Thermal imaging cameras and remote controls.
Check 12
Give a use of visible light in communication.
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Optical fibres carry signals as pulses of light.
Check 13
Give two uses of ultraviolet.
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Security marker pens and sterilising water.
Check 14
Why are X-rays used to image bones?
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Bone absorbs X-rays but soft tissue transmits them.
Check 15
Give two uses of gamma rays.
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Sterilising medical equipment and treating cancer.
Check 16
What is the hazard of microwaves?
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They can heat water in body cells.
Check 17
What are the hazards of ultraviolet?
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Skin ageing, an increased risk of skin cancer and eye damage.
Check 18
Why are X-rays and gamma rays called ionising?
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They carry enough energy to remove electrons from atoms, which can damage DNA.
Check 19
What can ionising radiation cause?
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Gene mutations and cancer.
Check 20
In what unit is radiation dose measured?
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Sieverts.
Check 21
Higher tier: how are radio waves produced?
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By oscillations in electrical circuits, such as an alternating current in an aerial.
Check 22
Higher tier: what produces gamma rays?
Show answer
Changes in the nucleus of an atom.
Keep going with The electromagnetic spectrum
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