Skip to main content

Wave nature of Electromagnetic Radiations

 Wave nature of Electromagnetic Radiations


Maxwell , in 1873 , showed theoretically that an oscillating electrical circuit should radiate electromagnetic waves propagating with the velocity of light. 


The main features of this theory are :

1. Energy may be emitted from any source such as heated rod or filament of a bulb through which electric current is passed. Energy is emitted continuously in the form of radiations (waves). 

2. These waves are associated with oscillating electric field and magnetic field. These two fields are perpendicular to each other and perpendicular to the direction of propagation of the radiation as shown in the figure. 


Fig: Oscillating electric and magnetic fields emitted by charged particles. 


3. The radiations possess wave nature. Their velocity is equal to the velocity of light, i.e, 3×10⁸ m/sec. The radiations are called electromagnetic radiations or electromagnetic waves. 

4. Electromagnetic waves do not require any material medium for propagation. This rays of sun reach us through space. Space does not have material medium. But sound waves require medium and can not move in vacuum. 


Summary:

This suggested that light consisted of electromagnetic waves of extremely short wavelength. Fifteen years later, Hertz succeeded in producing short -wavelength waves of electromagnetic origin and showed that they possessed all the properties of light waves, such as reflection, refraction, polarization, etc. Thus Maxwell's electromagnetic theory of light was experimentally justified. 


Limitations of Electromagnetic Wave Theory

Electromagnetic wave theory explains the properties of light such as interference and diffraction etc. But this theory could not explain the following facts :

1. The phenomenon of black body radiation. 

2. The line spectra of atoms with special reference to hydrogen. 

3. The photoelectric effect. 

4. Variation of heat capacity of solids as a function of temperature. 


Labels:

Comments

Post a Comment

Please do not enter any spam link in the comment box.

Popular posts from this blog

Extra Dimensions : The String Theory

Introduction   The world as we know it has three dimensions of space - length,width  and  depth  and one dimension of time.  But there's the mind - bending possibility that many more dimensions exist out there. Beyond these three visible dimensions, scientists believe that there may be many more. The development of string theory in early 1988 from studies of the problem of supersymmetry breaking by Antoniadis et al. In fact ,the theoretical framework of superstring theory posits that the universe exists in ten different dimensions. These different aspects are what govern the universe, the fundamental forces of nature and all the elementary particles contained within. Theories that suggest extra dimensions predict that,in the same way as atoms have a low - energy ground state and excited high - energy states, there would be heavier versions of standard particles called Kaluza - Klein States , would have exactly the same properties as standard particles but w...
Post a Comment
Read more

Shape of the universe

 Introduction For as long as humans have been grazing at the night sky, the question of how far can see into it has fascinated astronomers. The revolutionary observations made by Edwin Hubble in the late 1920s were the first direct evidence that the universe was not static. The systematically increasing spectroscopic redshift observed in increasingly distant galaxies was a clear sign that the universe expands. Because the universe is expanding, the sphere of what we can see is not defined simply by the age of the universe multiplied by the speed of the light. This is because the universe is expanding ;the distance between every point of the fabric of spacetime is forever increasing, a growth that affects the paths of photons. For a long time this expansion was believed to be slowing down due to the combined gravitational pull exerted by all the matter in the universe. However, at the end of the 1990s the measured dimming of Type la supernovae with increasing redshifts revealed that...
Post a Comment
Read more