Question

Describe diffraction of light due to a single slit. Explain formation of a pattern of fringes obtained on the screen

Answer 1

Hey !!

Single slit diffraction is explained by treating different parts of the wave front at the slit as sources of secondary wavelets.

                      At the central point C on the screen, θ is ''zero''. All path differences are zero and hence all the parts of the slit contribute in phase and give maximum intensity at C.

At any other point P, the path difference between two edges of the slit is

   NP - LP = NQ    

                         asin θ ≈ aθ ∴ sin θ is small

Any point P, is direction θ, is a location of minima if

                          aθ = nλ                            

This can be explained by dividing the slit into even number of part. The path difference between waves from successive parts is 180° out of phase and hence cancel each other leading to a minima.

Any point P, in direction Q, is a location of maxima

          if dθ = ( n + 1/2 )λ

This can be explained by dividing the slit into odd number of parts. The contribution from successive parts cancel in pairs because of 180° phase difference. The unpaired pat produces intensity at P, leading to a maxima.

GOOD LUCK !!

Answer 2

When a beam of light falls on the slit and it forms bright and dark pattern alternatively with its size comparable to the wavelength, it is called diffraction due to single slit.

How single slit diffraction happens?

• A diminished unclear light can be noticed within the geometrical shadow of an object when a beam of light falls on the sharp edge of that object.
• The pattern becomes visible when the same experiment is performed when a monochromatic light passes through an aperture whose dimension can be comparable to the wavelength of light.
• If in front of the slit  a screen is placed then the bright and dark pattern in alternative fashion become visible.

Explanation of the formation of pattern of fringes obtained on the screen:

• In the diffraction due to single slit experiment, there is bending of light which is diffraction that causes light from a coherent source to interact with itself and form a diffraction pattern which is bright and dark alternative pattern.
• Thus, this formula helps in finding the formation of a pattern of a fringes obtained on the screen single slit, D

                                          sin θ = mλ,

for m = 1,−1,2,−2,3, . . .

θ is the angle proportionate to the direction of the light

m is the order of the minimum.

λ is the wavelength of light,

and, D is the slit width

Below is the picture showing the single slit experiment.