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what is diffraction , interference , polarization of light ?? ,........pls explain it in a easy and  understandable language.......       

Dear student,

Diffraction:

Diffraction is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings.

Interference:

When two light from different coherent sources meet together, then the energy distribution due to one wave is disturbed by the other.This modification in the distribution of the light energy due to super-position of two light waves is known as Interference of light.

Polarisation:

We know light is an electromagnetic wave with electric and magnetic vectors which are mutually perpendicular to each other and perpendicular to the direction of propagation of light. An unpolarized light have electric vector in all direction. When orientation of electric vector is restricted to one particular direction using polarizer, this phenomenon is called polarisation.

Regards

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Diffraction, interference, and polarisation can be understood in terms of the wave properties of light. All waves diffract and interfere — you can see this just as easily with water waves, sound waves in air, earthquake tremors and so on, as well as light. Ripple tanks are often used to demonstrate wave phenomena in water.

Diffraction is the tendency of a wave to spread out around obstructions. It’s why you can hear sounds even if there’s, say, a building between you and the sound source. You can see diffraction most clearly when a wave is passed through a small slit, comparable in width to the the wavelength:

Diffraction is often described in terms of the Hugens, or Huygens-Fresnal principle, whereby each point on the wavefront of a wave can act as a point source for further wave propagation. The modern explanation for light is different, but the end result is the same.

Interference is where two waves overlap and peaks and troughs either reinforce each other or cancel out often producing interference fringes. You can see both phenomena together here where a slightly wider slit produces diffracted waves from each edge of the slit, and these two waves subsequently interfere:

Polarisation is the direction of orientation of a transverse wave as it propagates. It’s also possible to have circular polarisation of a light wave where the wave precesses as it travels:

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Dear student,
 

The quantum theory of light is way above the scope of this help desk. However you can understand the concepts as, in interference, the two light waves super-impose over one another. And in diffraction, the light waves traveling interact with any object of size comparable to the wavelength of the light wave then it exchanges energy to that object and we say the wave to be diffracted or scattered. In polarization, we restrict the vibrating components of electric and magnetic field in a light wave. these phenomenons can be explained by wave theory of light because in them we have to consider the wave mechanics. Whereas in some phenomenons like photoelectric effect, we have to consider the particle nature. Actually all these particles called photons are not real particles they are just hypothesized to make mathematics easier as in quantum world we can only have discreet levels of energy which are taken as energy of these particles. Thus in phenomenons involving quantum mechanics we have to apply particle nature and in classical the wave nature is used.

Regards
 
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