GCSE Physics revision

Types of electromagnetic waves

Electromagnetic waves

AQA 4.6.2.1

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AQA student objectives

Learning pathway

ALL 🎯

Give examples that illustrate the transfer of energy by electromagnetic waves.

MOST 🎯🎯

Apply the specified scientific knowledge of types of electromagnetic waves to a relevant example.

SOME 🎯🎯🎯

Analyse an unfamiliar example of types of electromagnetic waves using the specified scientific ideas.

Revision summary

Read on screen, then print for Cornell-style active revision.

All electromagnetic (EM) waves are transverse waves, meaning they oscillate perpendicular to the direction of energy transfer.
In a vacuum, all EM waves travel at the same speed of 3imes108 m/s, regardless of their type.
When EM waves travel through different mediums, they change speed, which can cause refraction — a change in direction of the wave.

1. What Are Electromagnetic Waves?AQA

All electromagnetic (EM) waves are transverse waves, meaning they oscillate perpendicular to the direction of energy transfer.
In a vacuum, all EM waves travel at the same speed of 3imes108 m/s, regardless of their type.
When EM waves travel through different mediums, they change speed, which can cause refraction — a change in direction of the wave.

The electromagnetic spectrum is a continuous range of waves split into seven types:
radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Frequency and wavelength are inversely related, meaning as frequency increases, wavelength decreases.
Reading the spectrum from left to right, frequency increases and wavelength decreases.
Wavelengths range from several kilometres for radio waves to less than one thousandth of a nanometre for gamma rays.

2. The Electromagnetic SpectrumAQA

The electromagnetic spectrum is a continuous range of waves split into seven types:
radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Frequency and wavelength are inversely related, meaning as frequency increases, wavelength decreases.
Reading the spectrum from left to right, frequency increases and wavelength decreases.
Wavelengths range from several kilometres for radio waves to less than one thousandth of a nanometre for gamma rays.

Humans can only detect a small portion of the electromagnetic spectrum, known as visible light.
The different wavelengths within visible light correspond to the different colours we see, remembered using the mnemonic ROY G BIV: red, orange, yellow, green, blue, indigo, and violet.

A useful strategy is to start with visible light in the middle and work outwards in both directions.
Infrared sits just before red (lower frequency), and ultraviolet sits just after violet (higher frequency).
Ultraviolet, X-rays, and gamma rays are grouped on the right because they are all ionising radiations that can damage cells.
Microwaves and radio waves sit on the far left and are both commonly used in communication.

4. Memorising the Order of the SpectrumAQA

A useful strategy is to start with visible light in the middle and work outwards in both directions.
Infrared sits just before red (lower frequency), and ultraviolet sits just after violet (higher frequency).
Ultraviolet, X-rays, and gamma rays are grouped on the right because they are all ionising radiations that can damage cells.
Microwaves and radio waves sit on the far left and are both commonly used in communication.

Gamma rays can be emitted during radioactive decay.
Visible light, ultraviolet, and X-rays can be emitted when electrons drop down energy levels within atoms.
Infrared radiation is generated when the bonds holding molecules together vibrate.
EM waves are emitted by a wide variety of sources and can travel through the vacuum of space once emitted.

5. Sources of Electromagnetic WavesAQA

Gamma rays can be emitted during radioactive decay.
Visible light, ultraviolet, and X-rays can be emitted when electrons drop down energy levels within atoms.
Infrared radiation is generated when the bonds holding molecules together vibrate.
EM waves are emitted by a wide variety of sources and can travel through the vacuum of space once emitted.

When EM waves encounter a material, they can be reflected, absorbed, or transmitted.
In many real-world situations, a combination of reflection, absorption, and transmission occurs simultaneously depending on the wavelength and the material involved.