# Science Site

## Electromagnetic Waves

Electromagnetic Field

We know that electricity and magnetism can be static or not moving. An example of static electricity is rubbing a plastic ruler against your hair to charge it and attract bits of paper. An example of static magnetism is a simple magnet. But when either of them are dynamic or moving, they give rise to electromagnetic phenomenon.

Electromagnetic waves are produced when electric and magnetic fields pair together. These two fields act in directions perpendicular to each other as well as to the direction of wave propagation. Electromagnetic waves have a complete spectrum dedicated to them which depends on the frequency at which these waves operate.

### Wavelength and frequency

Typically, the characteristics of a wave can be determined with the help of its wavelength or frequency. They are related to each other and to wave speed, energy carried by the wave, amplitude, etc.  As the wavelength of the electromagnetic wave increases, the frequency decreases and so does the energy contained by the wave. All electromagnetic waves are transverse waves. In a transverse wave, the disturbance of the constituent particles is perpendicular to the direction of wave propagation.

### Spectrum of electromagnetic waves

Electromagnetic waves lie in an electromagnetic spectrum. It is has wide range of values of wavelength and frequency and the different types of electromagnetic waves are classified accordingly. Among the different kinds of electromagnetic waves, radio waves have the highest wavelength of about 100 kilometre and the gamma rays have the lowest wavelength of about 1 Pico meter. 1 Pico meter is equal to 10-12 m. Here are the different types of electromagnetic waves from the highest wavelength or lowest frequency to the lowest wavelength or highest frequency:

1. Radio waves: These are used to transmit communication information over long distances. They are typically used for mobile, television, satellite communication, etc.
2. Microwaves: These contain small amount of energy, which is sufficient enough to cook different kinds of food items. They are used to construct microwave ovens and in other scenarios.
3. Infrared: Infrared waves are used in various communication devices to transfer information. TV remote controls typically make use to infrared waves.
4. Visible light: Visible light or simply light is an important electromagnetic wave. It has a spectrum of its own in which various colors of the rainbow lie.
5. Ultraviolet waves: These are the part of the waves emitted by the sun, direct exposure to which can give rise to skin cancer because of the high amount of energy they contain.
6. X-rays: X-rays have sufficient energy to penetrate most of the objects. They are used to obtain images of bones in order to detect a deformity or damage.
7. Gamma rays: These have the highest energy of any electromagnetic wave in the spectrum. Gamma rays are used in the treatment of cancer, to kill the cancerous cells.

All electromagnetic waves travel with the speed of light. They do not need a medium to travel, unlike sound waves. They exhibit all other properties of waves as well such as reflection, diffraction, interference and superposition. Electromagnetic waves are important even in our day-to-day life.