Question

Nucleus and yellow light of wavelength 150 nm passes through two slits separated by 0.1mm. The interference pattern is observed on a screen 0.5m behind the slits. Find distance between bright fringes of orders 1 and 3

Answer 1

Hence the distance between first and third fringe is d = 0.015 m

Explanation:

We are given that:

• λ (wavelength of light) = 150 nm = 150 x
• Distance between screen and slit "D" = 0.5 m
• Distance between the slit "d" = 0.1 mm = 0.1 x      

The fringe formula is given below.

Fringe width : β = n λ D /d

where :

"n" represents the number of fringes.            

3 β = 3 x 150 x  x 0.5 / 0.1 x

3 β = 2250 x  m

3 β = 0.02 m    (This is the width of third fringe)

β = 150 x  x 0.5 / 0.1 x  = 750 x m

Distance between first and third fringe  = 3 β - β

Distance between first and third fringe  = 0.015 m