Test: Interference Of Light


10 Questions MCQ Test Physics Class 12 | Test: Interference Of Light


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QUESTION: 1

In an interference experiment monochromatic light is replaced by white light, we will see:​

Solution:

white light is made up of seven colors VIBGYOR. All the seven colors will show interference, we can treat each color separately as a monochromatic light and study their interference separately. Each light will have their bright and dark fringes separately but at y=0 i.e for a center, each lights bright fringe will coincide. Two or more lights may have their bright and dark Fringe together or bright for one and dark for others may coincide depending upon the situation.

QUESTION: 2

If the Young’s apparatus is immersed in water, the effect on fringe width will​

Solution:

When Young's double-slit set up for interference is shifted from air to within water then the fringe width decreases because the refractive index of water is more than that of the air.
Originally the fringe width is given by:
β1​=λD/2d​
The new fringe width within water will be given by 
β2​= λD​/2nd
So, β2​= β1/n​​
Here, n is the refractive index of medium.
 

QUESTION: 3

Two coherent sources produce a dark fringe when phase difference between the interfering waves is(n integer)​

Solution:

Dark fringes will be produced when there are destructive interference. The condition for that is the two waves should have a phase difference of an odd integral multiple of π.

QUESTION: 4

In Young’s double slit experiment, the distance between the two slits is halved and the distance of the screen from the slit is doubled. The fringe width will be

Solution:

Fringe width β=λD/d​
On d′=d/2​, D′=2D
New fringe width β′= λD′​/d′=4β

QUESTION: 5

Young’s double slit experiment is carried out using two bulbs instead of using two slits and one source. Then​

Solution:

We observe interference pattern when the size of the slits are comparable to the wavelength of light. But here, the size of the bulb is bigger than wavelength of light.

QUESTION: 6

In the Young’s double slit experiment, the distance of p th dark fringe from the central maximum is:

Solution:

Position of the pth dark fringe is at a distance of 
y=(2p−1) (λD/2d)​ from the centre
where 
λ: Wavelength
D: Distance between slits 
d: slit width

QUESTION: 7

In Young’s double slit experiment, one slit is covered. The observed effect will be

Solution:

Because Presence of two coherent sources of radiation is one of the PRIME CONDITIONS FOR INTERFERENCE.

QUESTION: 8

When viewed in white light, a soap bubble shows colours because of

Solution:

When the light is incident on a soap bubble of certain thickness it constructively interferes for wavefronts which are in phase to produce white light and when the wavefronts are out of phase, they undergo destructive interference to produce a series of colors. Thus, interference is the reason.

QUESTION: 9

Two coherent sources of intensity ratio 100:1 interfere. The ratio of interference at the maxima and minima​

Solution:

We know that for two coherent sources, the intensity of their maxima is (Imax +  Imin)2 and that of its minima is (Imax +  Imin)2 . Thus we get the intensity of maxima = 121k and that of minima = 9k, for some constant k as (Imax = 100k and  Imin = k.
Thus we get the ratio as 121:81.

QUESTION: 10

Which of the following in conserved when light waves interfere?

Solution:

Interference is a known phenomenon in which two coherent sources of light meet and produce a resultant effect, i.e either a wave of greater or lower amplitude.
The intensity and amplitude changes depending on whether it's constructive or destructive interference. However, energy is distributed equally and hence remains conserved.

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