Electromagnetic waves are formed when an electric field comes in contact with a magnetic field. The electric field and magnetic field of an electromagnetic wave are perpendiculars (at right angles) to each other. They are also perpendicular to the direction of the EM wave
An electromagnetic wave can pass through the air, a solid material or vacuum. This wave does not need a medium to propagate or travel from one place to another. Mechanical waves (like sound waves or water waves) need a medium for travel. Electromagnetic waves are ‘transverse’ waves. Transverse waves are measured by their amplitude or height and wavelength or the distance between the highest/lowest points of two consecutive waves.
The highest point of a wave is known as ‘crest’, whereas the lowest point is known as ‘trough’. Electromagnetic waves can be divided into a range of frequencies. This is known as the electromagnetic spectrum. Examples of EM waves are radio waves, microwaves, infrared waves, X-rays, gamma rays, and much more.
Electromagnetics are used in our everyday life. There are several important technologies in our daily life are
- Electric power generator
- Electric motor
- Radio and T.V. broadcasting
- Satellite T.V.
- Cell phones and mobile phones
- Wireless LAN
- Cable T.V.
- Microwave oven
In electric power generator, it converts motion energy into electromagnetic energy and electric motor converts it back.
Microwave oven converts electromagnetic energy with low frequency into electromagnetic energy with very high frequency, which is comparatively easy to be absorbed by food and converted to heat.
The remaining applications use electromagnetic wave for transfer information. The receiver that uses an antenna is for collect electromagnetic wave and carries data from the air. Due to the weak power, an amplifier is used to convert weak power to strong and demodulator pick up data from high-frequency electromagnetic energy. This is in the case of radio, TV, satellite TV, GPS, cell phones and wireless LAN. Cable TV does not need antennas for transmitting electromagnetic wave via cables.