6.2.1 Electromagnetic (EM) Waves

Properties of EM Waves

• Electromagnetic waves are defined as:

Transverse waves that transfer energy from the source of the waves to an absorber

• All electromagnetic waves share the following properties:
• They are all transverse
• They can all travel through a vacuum
• They all travel at the same speed in a vacuum
• There are 7 types of electromagnetic waves, which all together form a continuous spectrum

The EM Spectrum

• The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies
• This order is shown in the diagram below from longest wavelength (lowest frequency) to shortest wavelength (highest frequency)

Visible light is just one small part of a much bigger spectrum: The electromagnetic spectrum

• The higher the frequency, the higher the energy of the radiation
• Radiation with higher energy is:
• Highly ionising
• Harmful to cells and tissues causing cancer (e.g. UV, X-rays, Gamma rays)
• Radiation with lower energy is:
• Useful for communications
• Less harmful to humans

Visible Light

• Visible light is defined as the range of wavelengths which are visible to humans
• Visible light is the only part of the spectrum detectable by the human eye
• However, it only takes up 0.0035% of the whole electromagnetic spectrum
• In the natural world, many animals, such as birds, bees and certain fish, are able to perceive beyond visible light and can see infra-red and UV wavelengths of light
• The different colours of waves correspond to different wavelengths:
• Red has the longest wavelength (and the lowest frequency and energy)
• Violet has the shortest wavelength (and the highest frequency and energy)

The colours of the visible spectrum: red has the longest wavelength; violet has the shortest

Exam Tip

To remember the colours of the visible spectrum either remember:

• The name “Roy G. Biv”
• Or the saying “Richard Of York Gave Battle In Vain”

The electromagnetic spectrum is usually given in order of decreasing wavelength.

Remember:

• Radios are big (long wavelength)
• Gamma rays are emitted from atoms which are very small (short wavelength)

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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