Electromagnetic Waves: The Ability To Briskly Travel Through
The electromagnetic waves (EM waves) are transverse in nature. The changes in the electric field or the magnetic field represent the wave disturbance in the EM waves. EM waves are the waves which have the ability to travel through the vacuum of the outer space. They are created due to the vibration of an electrical charge.
These are the waves that get propagated due to the simultaneous variations of the electric and magnetic field intensity. These include radio waves, visible light, infrared, ultraviolet, X-rays, gamma rays.
They move at a very constant speed of 3×108 m/s. They are also known as electromagnetic light, EM radiation or photons.
Uses Of Electromagnetic Waves
- They are used to transmit short or long or FM wavelength radio waves.
- They are used to transmit TV or telephone or wireless signals and energies.
- They are responsible for the transmission of energy in the forms of microwaves, visible light, infrared radiation, ultraviolet light, gamma rays and also X-rays.
The behaviour of an electromagnetic wave in any element is subject to its frequency or wavelength. The changing patterns of various sets in the electromagnetic spectrum make them ideal for a variety of uses as mentioned below.
Radio waves are mostly used for communications, be it television or radio. As radio waves are transmitted easily through air, it does not cause damage to the human body even if it absorbs it, and can be easily reflected to change its direction. These very attributes make them apt for communications. Radio waves are generally produced by oscillations in an electrical circuit. When radio waves are plunged by a conductor, they create an alternating current, that has the same frequency as the radio waves. The conductor could be an aerial on a radio, wherein, information is coded into the wave before transmission, which is decoded upon receiving the wave. Television and radio systems use this principle to broadcast information.
Microwaves are not only ideal for cooking food, but are ideal for satellite
communications as well. These microwaves have such high frequencies that are easily absorbed by molecules in food. The internal energy of the molecules is increased whenever microwaves are absorbed, causing heating. As microwaves can easily pass-through atmosphere, in the same way, it can pass between stations on Earth and satellites in the orbit.
Infrared light is used by electrical heaters, cookers for cooking food, and by infrared cameras which detect people in the dark. Infrared light has such types of frequencies that are absorbed by some chemical bonds. When the internal energy of the bonds increases, it absorbs infrared light, which resultingly causes heating. Because of this, infrared light is used for electrical heaters and cooking food. All objects emit infrared light. Although, the human eye is not able to see this light, but the infrared cameras detect these infrared lights. This ‘thermal imaging’ is useful for detecting people in the dark.
Visible light is the type of light that can be seen by humans as well. It is used in fibre optic communications, where coded pulses of light travel through glass fibres from a source to a receiver.
Ultraviolet radiation kills the bacteria that are there in water. This very process sterilises the water, thus making it safe to drink. Ultraviolet radiation is also good for skin as it aids in generating vitamin D. However, too much exposure to UV radiation can ultimately cause problems to the skin.
Hazards of Electromagnetic Radiation
Although, electromagnetic radiation has many advantages, yet, some of the waves can have hazardous effects on human body tissues. Ultraviolet waves, X-rays and gamma rays are various types of ionising radiation which means that they can blow up the electrons from the shells of atoms, turning them into ions. This process of ionisation can actually lead to mutations in cells, whose end result can lead to cancer.
Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer. Gamma rays can also damage or kill the cells in a person’s body. In order to be safe, exposure to ionising radiation needs to be kept as low as possible, especially for people who work with this type of radiation every day in hospitals. A radiographer using X-rays in a hospital has to stand behind a lead shield or be in another room when the X-ray machine is being operated.
Radio stations change sound to EM waves and then your radio receiver changes the EM waves back to sound waves again. Each station broadcasts at a certain frequency which can be tuned in by choosing their frequency. Carrier wave is the frequency of the EM wave that a station uses. Microphones convert sound waves to a changing electric current or electronic signal containing the words and music.
Different Radio Stations
The modified carrier wave vibrates electrons in the station’s antennae creating a radio wave that travels out in all directions at the speed of light to radio antennae. The vibrating electrons produce a changing electric current which radio separates the carrier wave from the signal to make the speakers vibrate creating sound waves.
Cell phones and cordless telephones are transceivers, device that transmits one signal and receives another radio signal from a base unit. One can talk and listen at the same time because the two signals are at different frequencies.
Thousands of satellites orbit Earth. A radio or TV station sends microwave signals to the satellite which amplifies the signal and sends it back to a different place on Earth. Satellite uses different frequencies to send and receive.
Global Positioning System
GPS is a system of 24 satellites, ground monitoring stations and portable receivers that determine exact location on Earth. GPS receiver measures the time it takes for radio waves to travel from 4 different satellites to the receiver. The system is owned and operated by the US Department of Defense, but the microwaves can be used by anyone.
Properties Of Electromagnetic Waves
- The EM energy is clean. We are not degrading the environment or destroying it to derive the raw material.
- It is also renewable.
- It is versatile in nature.
- The frequency, wavelength and the speed of light follow a relationship of:
Wavelength* frequency= speed of light