There are seven members of electromagnetic family. Arranged in order of decreasing wavelength (and increasing frequency): radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays and gamma-rays, see Figure 6.6. The types of radiation that occur in different parts of the spectrum have different uses and dangers - depending on their wavelength and frequency.

Radio waves

Radio waves have the longest wavelengths of all the electromagnetic waves. They range from about 1m to 300m. Radio waves are used primarily for communications, to transmit data such as television and radio, mobile phones, radar, Wi-Fi, Bluetooth, satellites, and computer networks. They are generated by electronic devices and are used in radio and communication system.

Microwaves

Microwaves fall in the range of the electromagnetic spectrum between radio and IR. They have frequencies from about 3 GHz to 30 THz, and wavelengths of about 10-1000mm. We use microwaves to cook food, satellite communication, and in radar that helps to predict the weather.

Infrared

Beyond the red end of the visible spectrum is infrared radiation. This ranges from 700nm down to 0.1cm and has frequencies from about 30 to 400 THz. We feel such radiation from a heat lamp but we cannot see this radiation. It is used for photography, medicine, military techniques, optical fiber communication, TV remote control and others. Anything that gives off heat radiates infrared waves.

Visible light

The visible light spectrum covers the wavelengths that can be seen by the human eye. This is the range of wavelengths from 380 to 700 nm which corresponds to the frequencies 430 × 10¹² Hz - 790 × 10¹²Hz.

Our eyes detect visible light. Visible light is used for seeing, photography, optical fiber and communication. Fireflies, light bulbs, and stars all emit visible light.

Ultraviolet

Ultraviolet (UV) light is the range of the electromagnetic spectrum between visible light and X-rays. It has frequencies of about 8 × 10¹⁴ to 3 x 10¹⁶ Hz and wavelengths of about 10 to 380 nanometers. This light is used in medicine and industrial applications. It is also used in detecting forged bank notes, helps to make vitamin D, hardening some types of dental filling and in nightclubs. UV is also dangerous for living things (plants or animals). Ultraviolet rays from the Sun cause sunburns. We are protected from the Sun’s ultraviolet rays by the ozone layer in Earth’s atmosphere..

X-rays

X – rays are produced by X – ray tube or machines. The wavelength of X – rays are in the interval 10 - 0.01nm. It is used in medicine and testing of materials. They can penetrate soft tissue like skin and muscle and are used to take X-ray pictures of bones in medicine. A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag.

Gamma (γ) rays

are electromagnetic waves having wavelengths from 0.1 – 10nm. Doctors use gamma-ray imaging to see inside your body. Gamma rays are used to Kill cancer cells, sterilizing medical equipment, killing bacteria to prolong shelf life of fruit. Gamma radiation causes damage to living tissue, which makes it useful for killing cancer cells when applied in carefully measured doses to small regions. Uncontrolled exposure, though, is extremely dangerous to humans. Gamma rays are produced in high energy nuclear explosions.

As the wavelengths of electromagnetic waves get shorter, their frequency and energy increases. Gamma rays are the shortest waves in the spectrum and, as a result, have the most energy.