The electromagnetic spectrum Cambridge IGCSE Physics revision
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In plain words
Light is one member of a big family of waves that all travel at the same speed in a vacuum: the electromagnetic spectrum. From longest wavelength to shortest they are radio, microwave, infrared, visible, ultraviolet, X-ray and gamma. The shorter the wavelength, the higher the frequency, and the more energy and danger.
Three things to know
- In order of increasing frequency: radio, microwave, infrared, visible light, ultraviolet, X-rays, gamma rays. Wavelength decreases along the same list.
- All electromagnetic waves are transverse and travel at the same speed in a vacuum: 3.0 × 10⁸ m/s.
- Higher frequency waves carry more energy and do more harm: ultraviolet damages skin and eyes; X-rays and gamma rays can damage cells and cause cancer.
Tips and tricks
- A sentence for the order: "Rabbits Mate In Very Unusual eXpensive Gardens" (Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma).
- Learn one use and one danger for each. Mark schemes want specifics: "X-rays image bones, and can damage cells".
It lands in your notebook with its questions as flashcards.
The electromagnetic spectrum: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which electromagnetic wave has the longest wavelength?
Radio waves are at the low-frequency, long-wavelength end.
Which has the highest frequency?
Gamma rays are at the top of the spectrum.
What do all electromagnetic waves have in common?
They all travel at 3.0 × 10⁸ m/s in a vacuum.
Which wave is used by a television remote control?
Remote controls send pulses of infrared.
Which part of the spectrum comes between visible light and X-rays?
The order is visible, ultraviolet, X-rays, gamma.
Why are gamma rays used to sterilise medical equipment?
Their high energy destroys living cells.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 9 marks. Write your answers on paper, then check them.
The electromagnetic spectrum
Cambridge IGCSE Physics 0625 · 9 marks · papermunch.org
Name ______________________________ Date ______________
State two properties that all electromagnetic waves have in common.[2]
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They are transverse, and they travel at the same speed in a vacuum. (Also: they can travel through a vacuum; they transfer energy.)
Give one use of microwaves and one use of X-rays.[2]
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Microwaves: cooking, or satellite and mobile phone signals. X-rays: imaging bones, or security scanners.
Calculate the wavelength of a radio wave of frequency 1.0 × 10⁸ Hz. Speed of light = 3.0 × 10⁸ m/s.[3]
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3.0 m. λ = v ÷ f.
Explain why people are advised to wear sunscreen.[2]
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Ultraviolet radiation from the Sun damages skin cells and can cause skin cancer; sunscreen absorbs it.
Answers: The electromagnetic spectrum
- 1. They are transverse, and they travel at the same speed in a vacuum. (Also: they can travel through a vacuum; they transfer energy.)
- 2. Microwaves: cooking, or satellite and mobile phone signals. X-rays: imaging bones, or security scanners.
- 3. 3.0 m. λ = v ÷ f.
- 4. Ultraviolet radiation from the Sun damages skin cells and can cause skin cancer; sunscreen absorbs it.