Question

Red light of wavelength 633 nm from a helium-neon laser passes through a slit 0.320 mm wide. The diffraction pattern is observed on a screen 2.60 m away. Define the width of a bright fringe as the distance between the minima on either side.

Answer 1

Answer:

$W = 10.28\ mm$

Explanation:

Given,

Red light wavelength = 633 nm

width of slit = 0.320 mm

distance,d = 2.60 m

Condition of first maximum

$a sin \theta_1 = m\lambda$

$\theta_1 =sin^{-1}(\dfrac{m\lambda}{a})$

m = 1

$\theta_1 =sin^{-1}(\dfrac{633\times 10^{-9}}{0.32\times 10^{-3}})$

$\theta_1 = 0.1133^\circ$

Width of the first minima

$y_1 = L tan \theta_1$

$y_1 = 2.60\times tan( 0.11331)$

$y_1 = 5.14 \ mm$

Now, width of the central region

$W = 2 y_1$

$W = 2\times 5.14$

$W = 10.28\ mm$