In Young’s experiment interference bands were produced on a screen placed at 150 cm from two slits, 0 . 15 mm apart and illuminated by the light of wavelength 6500 A o . Calculate the fringe width.

Given that Distance of screen, D = 150 cm = 150 × 10 - 2 m distance between slits, d = 0 . 15 mm = 0 . 15 × 10 - 3 m wavelength λ = 6500 A o = 6500 × 10 - 10 m Expression for fringe width, X = λ D d = 6500 × 10 - 10 × 150 × 10 - 2 0 . 15 × 10 - 3 X = 65 × 10 - 7 m X = 6 . 5 × 10 - 6 m = 6 . 5 μm Hence fringe width is 6 . 5 μm

In interference pattern, using two coherent sources of light; the fringe width is ____.

directly proportional to wavelength

inversely proportional to square of the wavelength

inversely proportional to wavelength

directly proportional to square of the wavelength.

State the conditions to get constructive and destructive interference of light.

Interference is a phenomenon in which two waves combine to generate a new wave with a smaller, larger, or equal amplitude. When the phase difference between the waves is an even multiple of π ( 180 ° ) , or path difference is even multiple of λ 2 , then constructive interference of light occurs. It forms bright fringes. When the phase difference is an odd multiple of π ( 180 ° ) , or path difference is odd multiple of λ 2 , then destructive interference occurs. It forms dark fringes.

Two coherent sources of light having intensity 81 : 1 produce interference fringes. Calculate the ratio of intensities at the maxima and minima in the interference pattern.

Two coherent sources of light having intensity 81 : 1 produce interference fringes. To calculate the ratio of intensities at the maxima and minima in the interference pattern. We have, I 1 = I 0 , I 2 = 81 I 0 The maximum intensity is given by: I m a x = I 1 + I 2 + 2 I 1 I 2 cos 0 = ( I 1 + I 2 ) 2 = 100 I 0 Similarly, the minimum intensity is given by: I m i n = I 1 + I 2 + 2 I 1 I 2 cos 180 = ( I 1 - I 2 ) 2 = 64 I 0 The ratio of intensities at the maxima and minima in the interference pattern = 100 64 = 1 . 5625

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 11 - Interference and Diffraction>Maharashtra Board-2019>Q 6

HARD

12th Maharashtra Board

IMPORTANT

Earn 100

Monochromatic light of wavelength 4300 Å falls on a slit of width ‘a’. For what value of ‘a’ the first maximum falls at 30°?

Important Questions on Interference and Diffraction

EASY

12th Maharashtra Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 11 - Interference and Diffraction>Maharashtra Board-2020>Q 7

A diffraction pattern is obtained by making blue light incident on a narrow slit. If blue light is
replaced by red light, then the diffraction bands _______.