The diagram below shows the electromagnetic spectrum:
It is a family of waves. Waves have the following properties: amplitude, wavelength, frequency and speed. Study the diagrams below, as some questions in this worksheet will be about the properties of waves. The speed of a wave is calculated using the following formula:
wave speed = frequency x wavelength
The electromagnetic spectrum is actually radiation emitted from the nucleus of an atom. The wavelength decreases as we go towards the gamma ray end of the spectrum. Gamma radiation and X-rays are used for screening, diagnosis and therapy. They are both very penetrating and can pass through the body to treat internal organs.
Nuclear radiation increases the risk of cancer due to causing ionisation, which means it changes the structure of atoms and, hence, living cells. However, it can be used to kill tumour cells after they are exposed to it through radiotherapy - for example, Cobalt-60, which is a very radioactive material that emits gamma radiation. It is also used to sterilise medical equipment.
When exposing tumour cells in the body to kill them, there is a danger of destroying healthy tissue, too. Therefore, treatment is set up in such a way so as to constantly send a large dose of radiation to the tumour but to only send intermittent, smaller doses to the surrounding healthy tissue.
Technetium-99m and Iodine-123 are two radioactive materials used for screening.
Microwaves are used for heating and cooking food, mobile phones, satellite TV and long distance communication. They penetrate about 1 cm into the outer layers of food. Microwave aerials are located on high buildings because transmitters and receivers have to be in 'line of sight'. Satellite dishes are microwave receivers which deliver satellite television channels. Satellites orbiting the Earth are in line of sight of a huge aerial on the ground, which handles a great number of phone calls and television pictures at the same time.
Infrared signals are used to make remote controls, wireless computer mice and security alarm sensors. Radio waves are also useful for wireless technology and the radio. They are reflected off solid surfaces, so sometimes provide signals in hard to reach areas.
Light has many uses, including communication, and can be sent with just a torch. This type of signal needs to be decoded. Visible light is the light from the Sun or even artificial light bulbs, which helps us see what is around us and different colours. We can only see the visible part of the electromagnetic spectrum, not the other waves.
That's quite a lot of information to take in, but studying the diagram of the electromagnetic spectrum at the top of this page will give you a visual picture of what's going on.
Are you ready to have a go at some questions now?