Electromagnetic waves/radiation are transverse oscillations (ripples) in electric and magnetic fields.
The visible spectrum shows the range of different frequencies (colours) of visible light waves (visible EM radiation).
In the visible spectrum, violet light has the highest frequency and refracts more than red as it slows more in glass.
The EM spectrum shows the range of frequencies that EM waves can have (radio, microwave, IR, visible, UV, X-ray, gamma).
EM waves in different frequency ranges have the same speed in air, but interact differently with different materials.

Keywords

Electromagnetic wave - Electromagnetic waves are oscillations/ripples in electric and magnetic fields.
Frequency - The frequency of a wave gives the number of oscillations that occur per second.
Spectrum - A spectrum is a continuous range or scale.
Refraction - Refraction is when waves enter a new material and change direction.
Radiation - Anything that is emitted (given out) from a system and transfers energy away from that system can be called radiation.

Common misconception

The different 'kinds' of EM radiation are different phenomena to each other and to visible light. Pupils may also think all radiation is dangerous, none is natural and that light is not radiation.

Each 'kind' of EM radiation is the same phenomena as light (i.e. waves/ripples in electric and magnetic fields) just with different frequencies and wavelengths. Try to refer to different frequencies/frequency ranges rather than different 'kinds'.

Pupils can use a ray box and prism to produce a spectrum. IR can be detected (and shown to be invisible) using a thermometer outside a spectrum, or by inviting pupils to hold their hand at a safe distance from a hot non-glowing object. Use a blacklight to show the fluorescence of many objects in UV.

Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.

The medium of a wave is ...

the speed of the wave.

the height of the wave.

Correct answer: the substance the wave travels through.

the distance from one crest to the next crest.

Q2.

A pupil draws a transverse wave on a piece of paper. The direction of wave travel is from left to right. Which of the following describes how each part of the medium moves as the wave passes through?

always from left to right

always from right to left

sometimes to the left and sometimes to the right

always upwards

Correct answer: sometimes upwards and sometimes downwards

Q3.

Which of the following describes the wavelength of a wave?

the height of a wave, from its centre line to a crest

the depth of a wave, from its centre line to a trough

Correct answer: the distance between one wave crest and the next wave crest

Correct answer: the distance between one wave trough and the next wave trough

Q4.

Which of the following describes the frequency of a wave?

the distance between one wave crest and the next

the height of a wave, from its centre line to a crest

the number of seconds it takes for a wavelength to pass a point

Correct answer: the number of wavelengths travelling past a point each second

Q5.

Which of the following is the wave equation?

speed = distance ÷ time

speed = time ÷ distance

Correct answer: speed = frequency × wavelength

speed = frequency ÷ wavelength

speed = wavelength ÷ frequency

Q6.

When a light ray travels from air to glass (and is not moving at right angles to the boundary), the ray bends …

towards the normal, because the light speeds up.

Correct answer: towards the normal, because the light slows down.

away from the normal, because the light speeds up.

away from the normal, because the light slows down.

Exit quiz

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6 Questions

Q1.

Which of the following colours of light has the highest frequency?

blue

indigo

red

Correct answer: violet

Q2.

White light is split into its separate colours by this triangular prism as some colours (frequencies) of light are refracted more than others. Which is refracted the most at each boundary, and why?

red, because its speed changes the most

red, because its speed changes the least

Correct answer: violet, because its speed changes the most

violet, because its speed changes the least

Q3.

A pupil makes waves on a rope. The speed of the waves is fixed by the properties of the rope, but the pupil can change the frequency. What happens to the wavelength if the frequency increases?

the wavelength increases

Correct answer: the wavelength decreases

the wavelength stays the same

Q4.

Put these electromagnetic waves in order of frequency, from lowest to highest.

1 - radio waves

2 - microwaves

3 - infrared

4 - visible light

5 - ultraviolet

6 - X-rays

7 - gamma rays

Q5.

Match each type of electromagnetic radiation with one of its uses.

Correct Answer:ultraviolet,Security pen ink can only be seen when this is shone onto it.

Security pen ink can only be seen when this is shone onto it.

Correct Answer:infrared,Thermal cameras detect this.

Thermal cameras detect this.

Correct Answer:radio,This is used to transmit television signals over long distances.

This is used to transmit television signals over long distances.

Correct Answer:X-rays,This is used to make images of a patient’s bones in hospital.

This is used to make images of a patient’s bones in hospital.

Q6.

Which of the following statements is correct?

All electromagnetic radiation made by humans is harmful.

All naturally-occurring electromagnetic radiation is harmless.

Correct answer: The Sun emits electromagnetic radiation in all seven frequency ranges.

The Sun emits only visible light, infrared radiation and ultraviolet radiation.