Electromagnetic Waves

Electromagnetic waves (such as light) form a continuous range called the electromagnetic spectrum.

Remember My Instructions, Visible Under X-ray Glasses.

Radio waves, microwaves and infrared rays all have a longer wavelength and a lower frequency then visible light. Whilst ultraviolet waves, x-rays and gamma rays all have a shorter wavelength and a higher frequency than visible light.

Electromagnetic waves can be reflected and refracted. Different wavelengths of electromagnetic waves are reflected, absorbed or transmitted differently by different substances and types of surface. E.g white surfaces are poor absorbers and emitters of Infrared radiation.

When a wave is absorbed by a substance the energy it carries is absorbed making the substance heat up. It may also create an alternating current of the same frequency as the radiation.

Light is one type of electromagnetic wave.

The seven colours of the rainbow form the visible spectrum (part of the spectrum visible to the human eye). It is the only part we can see.

It is produced because white light is made up of many different colours. These are refracted by different amounts as they pass through a prism-red light is refracted the least and violet the most.

Visible light can be used for communication, vision and photography.

Radiowaves:

Uses: Transmitting radio and t.v signals between places

Effects: High levels of exposure for short periods can increase body temperature leading to tissue damage, especially to the eyes.

Microwaves:

Uses: Satellite communitcation and mobile phone networks. Cooking and Bluetooth devices.

Effects: Cells can be damaged or killed.

Infra-red rays:

Uses: Grills, toasters and radiant heaters, remote controls for televisions and video recorders, optical fibre communication

Effects: Absorbed by skin as heat, excessive amount can cause burns.

Ultraviolet rays:

Uses: Security coding, subathing and sunbeds

Effects: Passes through skin to tissues below, high doses can kill cells, low doses can cause skin cancer

X-rays:

Uses: producing shadow pictures of bones and metals, can help treat some cancers. (radiotherapy)

Effects: Passes through soft tissues, some is absorbed. High does kills cells and low doses cause cancer.

Gamma rays:

Uses: Kills cancerous cells and bacteria on food and surgical instruments.

Effects: Passes through soft tissues, some is absorbed. High does kills cells and low doses cause cancer