Electro-Magnetic Waves

When light is passed through a prism, it is separated into all colors of rainbow, which is known as visible spectrum.

Theory of EM spectrum

There are some properties of light which can be explained by particle nature and other by wave nature. The initial explanations of light said that light consists of tiny particles which they call photons, which travel at a speed of light. When these particles hit something, they get bounced, absorbed or reflected back. When the bounce off from something and enter our eyes, we are able to see something.  The above descriptions could not satisfactorily explain why some photons are absorbed and others are reflected.

The theory of Electromagnetic spectrum tried to solve this dilemma. It is based upon the hypothesis that light is made up of waves. This theory has been used to explain that longest wavelength of the visible light (red) and shortest wavelengths of the visible light (blue) are absorbed by the green leaves (Chlorophyll) and green light is let reflected so that leaves appear green.

EM spectrum

The electromagnetic spectrum incorporates the range of all electromagnetic radiation, and extends from electric power at the long-wavelength end to gamma radiation at the short-wavelength end. In between, we find radio waves, infra-red, visible light, ultra violet and X-rays used in medical diagnostics. The following graphics shows the general properties of all the wavelengths of the electromagnetic spectrum. All of them are commonly known as Electromagnetic waves.

Electromagnetic waves are defined by their special characteristics, such as frequency, wavelength and amplitude.

Frequency

The frequency refers to the number of waves generated in a set period of time and is measured in Hertz (Hz). 1 Hz means one wave per second, 1 kHz (kilohertz) means one thousand waves per second, 1 MHz (megahertz) means one million waves per second, 1 GHz (gigahertz) means one billion waves per second and so on.

Wavelength

Wavelength is the distance between two waves. There is a fixed mathematical interrelation between the frequency and the wavelength. The higher frequencies have shorter wavelengths and the lower frequencies have longer wavelengths. The wavelength also indicates the ability of the wave to travel in space. A lower frequency wave can reach longer distances than a higher frequency wave. Radio waves are usually specified by frequency rather than wavelength.