Question 1

In Young's double slit experiment, using monochromatic light of wavelength , the intensity of light at a point on the screen where the path difference is , is K units. The intensity of light at a poin

Accepted Answer

Phase difference is related to path difference x by = 2 x. The intensity I at a point on the screen is given by I = I_ max ^2 ( 2 ). For x = , = 2 = 2 . Intensity I = I_ max ^2( ) = I_ max = K. For x = 3 , = 2 3 = 2 3 . Intensity I' = I_ max ^2 ( 3 ) = K ( 1 2 )^2 = K 4 . Answer: K 4

Question 2

In interference and diffraction, the light energy is redistributed. If it reduces in one region, producing a dark fringe, it increases in another region, producing a bright fringe. A. As there is no g

Accepted Answer

Statement A is true because interference and diffraction involve the redistribution of energy without any overall loss or gain, which is in accordance with the law of conservation of energy. Statement B is false because interference and diffraction are characteristic properties of all types of waves, including sound waves, water waves, and matter waves, not just light waves. Therefore, Statement A is true, but Statement B is false. Answer: A is true, but B is false

Question 3

An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then -

Accepted Answer

When unpolarised light is incident on a medium of refractive index 1.73 at Brewster's angle then reflected light is completely polarised. Using Brewster's Law aligned & = (i_p ) \ & 1.73= (i_p ) \ & i_p=60^ aligned By Law of reflection, i_p=r=60^

Question 4

The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at 22.5^ from the polarization axis of one of the polaroid, is ( I _0 is the intensity of polarised light

Accepted Answer

Initially two polaroids are crossed i.e. 90^ After passing from first polaroid intensity is I _0 aligned & I _0 4 ^2(2 ) \ & I _0 4 ^2(2 22.5) \ & I _0 8 aligned

Question 5

A beam of unpolarized light of intensity I_0 is passed through a polaroid A, then through another polaroid B, oriented at 60^ and finally through another polaroid C, oriented at 45^ relative to B as s

Accepted Answer

I_1= I_0 2 I_B= (I_1 ) ^2 60^ = I_0 2 ( 1 2 )^2= I_0 8 I_C=I_B ^2 45^ = I_0 8 ( 1 2 )^2= I_0 16

Question 6

Interference pattern can be observed due to superposition of the following waves: A. y=a t B. y=a 2 t C. y=a ( t- ) D. y=a 3 t Choose the correct answer from the options given below.

Accepted Answer

For interference pattem to be observed the sources must be coherent. Hence the superposition of waves y=a ( t) \& y=a ( t- ) would result in interference.

Question 7

An unpolarised light beam strikes a glass surface at Brewster's angle. Then

Accepted Answer

According to Brewster's law, reflected rays are completely polarized and refracted rays are partially polarized.

Question 8

Two slits in Young's double slit experiment are 1.5 mm apart and the screen is placed at a distance of 1 m from the slits. If the wavelength of light used is 600 10^ -9 ~m then the fringe separation i

Accepted Answer

Fringe width = Fringe separation ( )= D d = 600 10^ -9 1 1.5 10^ -3 = 6 10^ -7 1.5 10^ -3 =4 10^ -4 ~m

Question 9

If the monochromatic source in Young's double slit experiment is replaced by white light, then

Accepted Answer

At central point on screen, path difference is zero for all wavelength. So, central bright fringe is white and other fringes depend on wavelength as = D d . Therefore, other fringes will be coloured.

Wave Optics — Previous Year Questions & Solutions