The Electromagnetic spectrum
The electromagnetic spectrum is a generic term for everything covering electromagnetic radiation. Radio waves, light and radiation are different types of radiation in the electromagnetic spectrum.
Visible light, radio waves and X-rays are examples of electromagnetic radiation (EMR). EMR is energy transmitted through empty space or through matter as electromagnetic waves.
When an electrical charge changes its energy condition it leads to moving waves. These are waves of different frequency and wavelength dependent on the origin.
In the figure above, both the frequency and wavelength are included, and the correlation between these is given in the equation c = λ x f, where c is the speed of light, λ is wavelength and f is frequency.
Waves with a long wavelength spread well beyond their surroundings. Radio waves are used to transmit wireless signals to TVs, radios and mobile phones through the air.
Microwaves are less widespread and are used where the transmitter and the receiver are closer to each other. In this spectrum you will, for example, find radar and microwave ovens.
Physical bodies with temperatures around room temperature and above will emit radiation in the infrared area. This is radiation in the form of heat. Different cameras and surveillance equipment such as motion detectors can react to infrared radiation.
Visible light has a whole spectrum of colours. From the colour red with the longest wavelength (and thus least energy) to the colour violet which has the shortest wavelength (and the highest energy):
X-rays are energy rich radiation and can penetrate soft tissue. This type of radiation does not penetrate bones, and is therefore very suitable for photographing the skeleton of humans and animals.
Gamma radiation is very energy rich and penetrates most solid materials. Gamma rays are ionising radiation and can therefore destroy molecules and connections in atoms and cause damage to tissues.