tried to find out of what the thermal radiation is made. It is now a well-known fact that thermal radiations consist of electromagnetic waves of various frequencies or wavelengths. It is based on a number of modern concepts, which were unknown in the mid-nineteenth century. First active study of thermal radiation laws occured in the ’s and the theory of electromagnetic waves and the emission of such waves by accelerating charged particles was developed in the early ’s by James Clerk Maxwell, which was experimentally confirmed later by Heinrich Hertz.
Here, we will learn some facts about electromagnetic radiations. James Maxwell ( ) was the first to give a comprehensive explanation about the interaction between the charged bodies and the behaviour of electrical and magnetic fields on macroscopic level. He suggested that when electrically charged particle moves under accelaration, alternating electrical and magnetic fields are produced and transmitted. These fields are transmitted in the forms of waves called electromagnetic waves or electromagnetic radiation .
Light is the form of radiation known from early days and speculation about its nature dates back to remote ancient times. In earlier days (Newton) light was supposed to be made of particles (corpuscules). It was only in the 19th century when wave nature of light was established. Maxwell was again the first to reveal that light waves are associated with oscillating electric and magnetic character (Fig.
. ). Although electromagnetic wave motion is complex in nature, we will consider here only a few simple properties. (i) The oscillating electric and magnetic fields produced by oscillating charged Fig.
. The electric and magnetic field components of an electromagnetic wave. These components have the same wavelength, frequency, speed and amplitude, but they vibrate in two mutually perpendicular planes. particles are perpendicular to each other and both are perpendicular to the direction of propagation of the wave.
Simplified picture of electromagnetic wave is shown in Fig. . . (ii) Unlike sound waves or waves produced in water, electromagnetic waves do not require medium and can move in vacuum.
(iii) It is now well established that there are many types of electromagnetic