Light travels in waves. These waves are just one of seven types of electromagnetic waves (waves of energy associated with electric and magnetic fields produced when atoms or electrons lose energy) that make up the electromagnetic spectrum. All electromagnetic waves travel through space at the same speed (the speed of light) and do not require a supporting medium in which to travel. However, whilst all these waves travel at the same speed, their wavelengths and frequency vary since each carry different amounts of energy. The colours of the light spectrum (red, orange, yellow, green, blue, indigo and violet) are the only part of the electromagnetic spectrum that we can see, the rest are invisible. Infrared, microwave and radio waves all have longer wavelengths and carry less energy that visible light. Ultraviolet, x-ray and gamma rays have shorter wavelengths and carry more energy. All objects give off electromagnetic waves, from the largest solar body to the small speck on the earth, even our bodies.
Wave type | Wavelength | Properties | Uses |
Gamma rays | 1/100,000,000mm | Emitted by radioactive materials Can destroy cells and cause mutations. | Treating cancer Sterilisation of medical instruments and food. |
X-rays | 1/1,000,000mm | Absorbed by bones and teeth but passes through flesh. Dangerous in high doses. | Detecting broken bones, damaged teeth and diseases in the body. |
Ultraviolet rays | 1/10,000mm | Emitted by the Sun and other white-hot objects. Will pass through air but not solids. Can cause burning to the skin. | Sterilising materials. Sun beds. Marking goods to deter theft. |
Visible light | 1/1000mm | Light with differing wavelengths appear as different colours to us. | Artificial lighting. |
Infrared rays | 1/100mm | Emitted by all warm/hot surfaces. Can be detected by heat sensitive devices. | Heating and cooking. Tracking and locating objects at night, such as lost people. |
Microwaves | 10mm | Absorbed by some materials such as water. Reflected by metals. Passes through materials such as glass, paper and plastic. | Cooking and satellite communications |
Radiowaves | 10,000m | Can be transmitted around the Earth. | Carry radio and TV and communication signals. |