Bright bands positions
D = ml ;
m = 0, 1, 2, 3,------
For Constructive Interference
but = ml
Thus, Bright bands occur at
distances from the Central bright band at 'O'
Dark bands positions
but D = (2K + 1) l/2
, K = 0, 1, 2, 3, ..... For Destructive Interference
Thus, Dark bands occur at
from the central bright band t 'O'
Band width : X
From (4) or (5) it is obvious that
xm+1 - xm
= xk+1 - xk
where X = Distance between any consecutive or
is called band width.
Equation (6) can be re-written as
By using Young's double slit or Fresnel's Bi-prism
or Lloyd's single mirror method, the band width X and separation
d can be measured with the help of an optical bench, for a given
distance D and hence the wave length l
can be determined.
18.1 Interference of light
18.2 Diffraction of Light
18.3 Polarization of light