The concept of electromagnetic radiation came to know when Maxwell derived the four equations to correlate the electric field and magnetic field. With the help of these equations, he found that electric field and magnetic field depend on time and space propagate in the form of traverse waves. According to faraday law, when there is a change in magnetic flux it results in the induction of emf in the circuit. This implies that if magnetic flux causes the emf then surely there is an electric field. Based on this concept, Maxwell found that a time-varying magnetic field is a source of an electric field and vice-versa. Thus, we found that an accelerated charged particle is associated with both fields and this particle is the source of the electromagnetic field. From his theory, we knew that Light is also an electromagnetic wave.
As we know that both electric and magnetic field is in relation and the change in either field produce the other field. If we change the magnetic field, we get the electric field and if we vary the electric field then we get the magnetic field. We also found that changes in electric and magnetic fields are mutually perpendicular and show a wavelike nature. Thus on the behalf of these predictions, we get the definition of Electromagnetic Radiation.
Hence, electromagnetic radiation is radiation which is originated from an accelerated charged particle, and the radiation travel in space with coupled electric and magnetic fields where both fields are vibrating perpendicular to each other and also perpendicular to the direction in which radiation is traveling. We can see below the diagram, that E denotes the electric field and B denote the magnetic field.
In 1865, the first time its successful experiment was completed by Heinrich Hert proved the existence of Electromagnetic waves. After some years, Marconi transmitted the first electromagnetic radiation. This experiment was a revolutionary step in the field of wireless communication.
Electromagnetic spectrum is an orderly distribution chart of all electromagnetic radiation according to its wavelengths and frequency.
| SR.NO | Radiation | Wavelength | Frequency |
|---|---|---|---|
| 1 | Radio wave | $\mathrm{600m-0.1m}$ | $\mathrm{500kHz-1000MHz}$ |
| 2 | Micro Wave | $\mathrm{0.3m-10^{-3}m}$ | $\mathrm{10^{9}Hz-10^{12}Hz}$ |
| 3 | Infra-Red Radiations | $\mathrm{5\times 10^{-3}m-10^{-6}m}$ | $\mathrm{10^{11} Hz-5\times 10^{14}Hz}$ |
| 4 | Visible Light | $\mathrm{8\times 10^{-7}m-4\times 10^{-7}m}$ | $\mathrm{4\times 10^{14} Hz-7\times 10^{14}Hz}$ |
| 5 | Ultra-Violet | $\mathrm{3.5\times 10^{-7}m-1.5\times 10^{-7}m}$ | $\mathrm{10^{16} Hz- 10^{17}Hz}$ |
| 6 | X-rays | $\mathrm{100\times 10^{-10}m-0.1\times 10^{-10}m}$ | $\mathrm{10^{18} Hz- 10^{20}Hz}$ |
| 7 | Gamma Rays | $\mathrm{10^{-14} m- 10^{-10}m}$ | $\mathrm{10^{18} Hz- 10^{22}Hz}$ |
There are some important properties of Electromagnetic radiation in the below points.
As we know from the above definition that electromagnetic radiation is produced by an accelerated charge and does not need any material medium like metal, non-metal, etc for propagation.
The vibration of the electric and magnetic fields is in the same phase.
The direction of the Electric field and Magnetic field are perpendicular to each other and also perpendicular to the direction of wave propagation. That’s why electromagnetic radiations are transverse.
The speed of electromagnetic radiation is the same and equal to the speed of light in free space. But when it passes through a material medium, the speed of radiation can be calculated by
$$\mathrm{v=\frac{c}{\sqrt{\mu _{r}\varepsilon _{r}}}}$$
Electromagnetic Radiation has also linear momentum which is equal to
$$\mathrm{p=\frac{U}{c}}$$
Electromagnetic radiations are not deflected by both electric and magnetic fields.
The amplitude ratio of both electric and magnetic fields for Electromagnetic radiation is
$$\mathrm{\frac{E_{0}}{B_{0}}=C=\frac{1}{\sqrt{\mu _{0}\varepsilon _{0}}}}$$
Electromagnetic radiations have also the property of reflection, refraction, polarization, interference, and diffraction.
Electromagnetic radiation also has energy and that is equally shared by an electric field and magnetic field. Hence, the energy density of electromagnetic radiation is given by
$$\mathrm{u=u_{E}+u_{B}}$$
$$\mathrm{u=\frac{1}{2}\left [ \varepsilon _{0}E^{2}_{0} +\frac{B^{2}_{0}}{\mu _{0}}\right ]}$$
These electromagnetic radiations are very useful for our daily life, medical and industrial use. Here are a few important applications of EM radiation.
Radio waves are very important for communication systems as all the devices such as TV, Radio, etc are based on Electromagnetic radiation.
Radio waves are also used for Radioastronomy.
Microwaves are used for sensing in radar systems of aircraft and ships.
Microwaves are also used for long-distance communication like signal transferring to satellites.
At our home, we use microwave ovens which heat the food with microwave radiation.
Infra Red radiations are used by remotes to control appliances.
IR radiations are hot so these are used for the greenhouse effect for farming.
IR radiation is also used in night cameras for clear vision during dark or haze.
We can also use IR for muscle treatment and molecular structure determination.
Visible light is the most important part of electromagnetic radiation for a living being.
UV radiation can be used for food preservation, bacteria or virus killing, Fingerprint reading, etc.
X-rays are the most important form of electromagnetic radiation that serves in the field of medical science.
X-rays are also used for detecting metals like gold, diamond, weapons, etc.
Gamma rays are very important for cancer treatment and nuclear reaction ignition.
Also, polythene form ethylene is manufactured by using Gamma rays.
Electromagnetic radiation is very normal in our daily life. We are using lots of devices which work on electromagnetic radiations. Electromagnetic radiation is produced by both nature and humans. Along with several positive uses, these radiations are also affecting the environment and living beings. In the following bullet points, there is a detail of the effects.
we are using huge amounts of electromagnetic radiation for communication by smartphones, TV, etc. For this transmission we set up lots of towers that produce high-frequency waves that cause headaches, migraine, cancer, leukemia, etc.
These electromagnetic radiations also affect plants’ living cells and hurt growth.
For birds these electromagnetic radiations are very harmful. These radiations interfere with their natural sound signal to make meaning less causing communication breaking between male and female birds which decreases the birth rate. Also, high-frequency EM radiation affects the skin and eyes of birds.
Electromagnetic radiations also cause changes in the behavior and natural process like matting, fertility, etc within land and aquatic animals.
Day by day, for household and other industrial purposes humans are emitting Infrared, Gamma rays, and Uv rays which cause a change in the temperature of the earth's atmosphere. This contributes to Global warming.
The radiation associated with both electric and magnetic field are called electromagnetic radiation. Electromagnetic radiations are a very important innovation of technology. At present, we are using this phenomenon in every field. But, we should take care of limits so that it will not become a disaster.
Q1. What do you mean by wavelength?
Ans. The wavelength is the distance between two successive crests or troughs.
Q2. What do you mean by Frequency?
Ans. In simple words, frequency is the rate of happening any incident. By definition, the number of repetitions in unit time. Frequency is reciprocal to time.
Q3. What do you mean by Electromagnetism?
Ans. Electromagnetism is a branch of physics in which we study the cause and nature of forces that come into play due to the collaboration of electric and magnetic fields.
Q4. What is the velocity of electromagnetic radiation when they pass through a vacuum?
Ans. The velocity of electromagnetic radiation in a vacuum is equal to the velocity of light which is 3,00,000 km/second.
Q5. What is the energy of a photon?
Ans. According to the planks theory, the energy of a photon is directly proportional to the frequency of the photon.
$$\mathrm{E=hf}$$
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