# Electromagnetic waves for OCR GCSE Physics

1. Basics of electromagnetic waves
2. The Electromagnetic Spectrum
3. Uses of electromagnetic waves
4. Health and electromagnetic waves

Electromagnetic waves are transverse waves, so particles move perpendicular to the direction of energy transfer. Their oscillations are changes in electrical and magnetic fields which are in phase with each other and vibrate at 90° from each other.

Electromagnetic waves run along a spectrum of different wavelengths. All of these waves travel at the same speed in a vacuum, but the different frequencies and wavelengths means that each of the various waves on the spectrum have different properties.

The different properties of electromagnetic waves along the EM Spectrum mean that each type of wave can be used for different purposes. High energy waves are often used in medicine such as x-ray imaging and chemotherapy, whereas waves with long wavelengths tend to be used in communication. It is important to know a few purposes for each type of wave.

Exposure to certain types of electromagnetic radiation can cause a lot of damage to the body. The higher the frequency of the waves, the more damage they can cause to living things. UV, x-rays and gamma rays are types of ionising radiation – ionisation can have very hazardous effects on the body.

# 1

The human eye is only able to see a small range of wavelengths within the electromagnetic spectrum. How does the eye experience these different wavelengths in the visible light part of the spectrum?

The eye experiences different wavelengths as different colours. Red light has the longest wavelength and blue light has the shortest.

# 2

What is the range of frequencies in the waves of the EM spectrum?

from 10⁴ Hz to 10²⁰ Hz

# 3

X-rays are commonly used in hospitals to treat cancer. Name one other medical use of X-rays and explain why they are suitable for this purpose.

Any one from: CT scans, seeing bone fractures or detecting dental problems. X-rays are suitable because they can be picked up by photographic film, they are absorbed by bones and teeth, they are unaffected by soft tissue and they are able to be sent through the body in any direction.

# 4

Energy efficient lights use fluorescent materials to emit visible light. Explain how ultraviolet radiation is used in this case to produce visible light.

Fluorescent lights contain a source of UV radiation which is emitted when an electrical current flows through the light. The UV is reflected within the light by a white coating, as it is reflected it loses energy and can then be emitted as a visible light ray.

# 5

Which of the following is most damaging to the human body? Ultraviolet, x-rays or gamma rays.

gamma rays

End of page