Wave Optics - Diffraction Pattern

Description:

As we have interference pattern of alternate bright and dark fringes, similar to it we also have the diffraction pattern that generates bright and dark points on the screen.

Diffraction pattern contains a Central Maxima, Bright fringe and dark fringe.

• Conditions for Bright Points - θ is odd multiples of λ/2a;

  θ = 0,  

  3/2

  λ/a

  ,

  5/2a

  λ, (2n + 1)

  λ/2a

  Where n = 1, 2, 3, ……..

• Conditions for Dark Points − θ is even multiples of λ/a

  θ =

  λ/a

  ,

  2λ/a

  ,

  3λ/a

  Where n = 1, 2, 3, ……..

• Width of Fringes −

  Bright Fringe (W_B) −

  W_B =

  λD/a

Dark Fringe(W_D) −

W_D =    
λD/a

Central Bright Fringe W_CB −

W_CB =    
2λD/a

• The Central maxima is nearly 25% brighter than the first bright spot.

• The Central Maxima is so large and bright that other fringes are not visible to us, hence fringe cannot be viewed as brightness decreases rapidly.

Graphical representation of Diffraction pattern −