What is the electromagnetic spectrum, and what are the uses and hazards of each part?
The electromagnetic spectrum from radio waves to gamma rays, the shared properties of EM waves, and the uses and hazards of each region.
A focused answer to WJEC GCSE Physics topic 1.5 on the electromagnetic spectrum, covering the order from radio waves to gamma rays, the shared properties of EM waves, and the uses and hazards of each region from radio to ionising gamma.
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What this topic is asking
WJEC wants you to put the electromagnetic spectrum in order, state the properties all EM waves share, and give the uses and hazards of each region. This is part of topic 1.5 Features of waves in Unit 1 of WJEC GCSE Physics (3420).
The order of the spectrum
Shared properties of EM waves
Uses of each region
Hazards of each region
The danger of EM radiation depends on its frequency. The low-frequency end (radio, microwave, infrared) mainly heats tissue. Microwaves can heat internal body tissue; too much infrared causes skin burns. From ultraviolet upwards the radiation is ionising: it carries enough energy to knock electrons from atoms and damage cells. Ultraviolet can cause skin cancer and eye damage; X-rays and gamma rays are strongly ionising and can cause cancer or mutate cells, so exposure is carefully controlled.
Try this
Q1. Put these in order of increasing frequency: X-rays, radio waves, infrared. [1 mark]
- Cue. Radio waves, infrared, X-rays.
Q2. State one use of microwaves. [1 mark]
- Cue. Cooking food, or mobile phone and satellite communication.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20183 marksState three properties that all electromagnetic waves share.Show worked answer →
A topic 1.5 question. Award one mark each for any three of: they are all transverse waves; they all travel at the same speed in a vacuum (the speed of light, ); they can all travel through a vacuum (need no medium); they all transfer energy from a source to an absorber; or they all obey . Markers reward three distinct correct properties. A common error is to give a use rather than a shared property.
WJEC 20214 marksGive one use and one hazard each for ultraviolet and for gamma radiation.Show worked answer →
A topic 1.5 question. Ultraviolet: a use is security marking, fluorescent lamps or sun tanning (1 mark); a hazard is that it can cause skin cancer and eye damage with overexposure (1 mark). Gamma: a use is sterilising medical equipment, killing cancer cells or as a tracer in medicine (1 mark); a hazard is that it is strongly ionising and can cause cancer or cell mutation (1 mark). Markers reward one valid use and one valid hazard for each. A common error is to give a use as a hazard, such as saying gamma "treats cancer" as the hazard.
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Sources & how we know this
- WJEC GCSE Physics specification (3420) from 2016 — WJEC (2016)