Electromagnetic radiations are the energy radiations that possess a time-varying electric and magnetic field. The electric field, magnetic field, and the direction of wave propagation are aligned mutually perpendicular to each other. Electromagnetic waves move at the speed of light and are capable of travelling in a vacuum or free space. The ordered representation of electromagnetic waves is given by an electromagnetic spectrum. This spectrum includes all the electromagnetic radiations existing in nature, namely, gamma rays, x rays, ultraviolet radiations, visible rays, infrared radiations, microwaves, and radio waves. In the electromagnetic spectrum, the electromagnetic waves are properly arranged according to their wavelengths or frequency. The energy possessed by the gamma rays is the highest, whereas the energy possessed by the radiowaves is the lowest. Hence, the gamma rays are the high frequency and short wavelength radiations, while the radio waves are the low frequency and long wavelength radiations. According to modern quantum theory, an electromagnetic wave is a flow of photons through space.
Examples of Electromagnetic Waves
1. Radio and Television
Radio Waves are typically used for the purpose of signal broadcasting via various signal modulation techniques such as frequency modulation, amplitude modulation, etc. or directly with the help of satellites. Radio waves can travel through the air easily, which makes signal transmission simple. Also, they do not get absorbed by the obstacles present in the pathway, thereby making long-distance communication possible.
2. Microwave Ovens
As the name signifies, microwave ovens make use of high energy possessed by the microwaves to cook or heat the food. The frequency range of microwaves lies between 1 GHz to 1000 GHz. Microwaves get reflected on striking a metallic surface and get absorbed by the food. These properties make them useful in various kitchen appliances.
3. Medical Examination
A number of electromagnetic waves are used for medical diagnosis purpose. For instance, X-Rays are used to get an image of tissues and bones, thereby allowing the medical examiner to locate broken bones or injured body tissues. MRI or magnetic resonance imaging also makes use of electromagnetic waves for the purpose of detecting and curing tumours and other disorders.
The electromagnetic rays lying in the wavelength range of 80 nanometers to about 10 nanometers are known as UV rays or ultraviolet rays. It is experimentally verified that ultraviolet rays can kill bacterias. Hence, ultraviolet radiations are mostly used for the purpose of sterilization. When water is exposed to UV rays, the germs and bacteria get killed, and the water turns safe for drinking. UV rays are also used by doctors to sterilize surgical instruments and air in the operation theatre.
5. Communication Devices
A number of communication devices such as cellular phones, telephones, telegraphs, television, etc. make use of electromagnetic radiations to transmit and receive information. Microwaves are high-frequency electromagnetic radiations. This high frequency or high energy enables a microwave to travel through the atmosphere with great ease. Hence, microwaves are used for satellite communication. Similarly, other electromagnetic waves such as radio waves are used in cellular communication.
RADAR is an acronym for radio detection and ranging. RADAR is used in communication devices and to locate or measure an obstacle. Microwaves emitted by a RADAR bounce back upon hitting the target. The time taken by the wave to hit the obstacle and bounce back is noted. This observed time is then used to determine the exact location of the obstacle.
7. Military Equipment
Electromagnetic waves are utilized in constructing various safety equipment used in the military such as night-vision goggles, cameras, etc. A narrow coating of infrared rays is applied to the lens of the camera and the goggles. The IR coating enables the wearer to locate people in dark with the help of thermal imaging.
8. Cancer Therapy
Some of the electromagnetic radiations such as gamma rays have the ability to kill living cells. Due to this property of gamma rays, they are used in the medical industry in the treatment of cancer. When a cancerous cell or tissue is exposed to gamma rays, it gets eliminated, thereby curing the disease.
The frequency band of the electromagnetic spectrum that is easily visible constitute the visible light band. The visible light is used by photosynthetic organisms such as plants and trees to perform the process of energy generation known as photosynthesis. When the sunlight falls on the surface of photosynthetic organisms, the visible light gets absorbed, and the other frequency bands get reflected. The absorbed light, therefore, gets converted into chemical energy.
10. Electric Heaters or Cookers
Infrared light consists of a band of frequencies that get absorbed by coming in contact with certain chemical bonds. This absorption of infrared light increases the internal energy of the bonds, thereby releasing heat energy. Almost all the objects present on the earth are capable of emitting infrared radiations. Any object that can emit infrared waves can generate heat energy. Hence, infrared radiations can be used in appliances such as an electric heater, electric cooker, etc.