EM radiation is classified into types according to the frequency of the wave: these types include, in order of increasing frequency, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
Table 1 lists the wavelength and frequency ranges of the divisions of the electromagnetic spectrum.
Examples of some uses of electromagnetic waves are shown in Table 2.
Exercise 1: EM radiation
Arrange the following types of EM radiation in order of increasing frequency: infrared, X-rays, ultraviolet, visible, gamma.
Infrared, visible, ultra-violet, X-rays, gamma
Calculate the frequency of an EM wave with a wavelength of 400 nm.
Give an example of the use of each type of EM radiation, i.e. gamma rays, X-rays, ultraviolet light, visible light, infrared, microwave and radio and TV waves.
Gamma rays: Studying the physics of stars by observing gamma ray bursts in space
X-rays: Searching baggage at the airport
ultra-violet: Used in sun beds to help people get a tan during winter. NB! Dangerous!
Visible light: Used in Light Emitting Diodes for use as indicator lights in electronic equipment
infrared: Used for night-vision goggles, objects emit infrared radiation because they are warm and can therefore be detected at night using infrared goggles.
Microwaves: Microwave ovens emit microwave radiation that excites motion in water molecules in foodstuffs, thereby warming it up
radio waves: Use for telecommunication
TV waves: see radio waves.
EM radiation in the visible part of the spectrum is scattered off all of the objects around us. This EM radiation provides the information to our eyes that allows us to see. The frequencies of radiation the human eye is sensitive to constitute only a very small part of all possible frequencies of EM radiation. The full set of EM radiation is called the electromagnetic spectrum. To simplify things the EM spectrum divided into sections (such as radio, microwave, infrared, visible, ultraviolet, X-rays and gamma-rays).
Radio waves, microwaves and infrared radiation
The EM spectrum is continuous (has no gaps) and infinite. Due to technological limitations, we can only use electromagnetic radiation with wavelengths between 10−14 m and 1015 m.