Question

A Fraunhofer diffraction pattern is produced by a light of wavelength 5000 Å. The focal length of the lens is 20 cm and the slits are 0.3 mm wide. Calculate distance of the second dark band and of the next bright band from the axis.

Answer 1

Hello friends

I am here to help you

for the dark fringe in diffraction we can say

here given that

n = 1 for first dark fringe

a = width of the slit

now for finding the angle it is given

for small angles we can write

now by above equation we can find

so width of the slit is 0.12mm

Answer 2

Hello friends

I am here to help you

for the dark fringe in diffraction we can say

here given that

n = 1 for first dark fringe

a = width of the slit

now for finding the angle it is given

for small angles we can write

now by above equation we can find

so width of the slit is 0.12mm