Engineering Physics Question Paper focuses on “Production of Circular and Elliptically Polarized Light”.
1. By using Nicol prism, the emergent beam is ____________
a) Plane polarized
b) Elliptically Polarized
c) Circularly polarized
d) Unpolarized
Answer: a
Clarification: When an unpolarized beam is incident on a Nicol prism, it splits into two components – ordinary and extraordinary. The ordinary components are internally reflected and the emergent beam is plane-polarized.
2. What should be the phase difference between the two plane-polarized waves, vibrating at right angles to each other, to produce circularly polarized light?
a) π/6
b) π/2
c) π/4
d) π/3
Answer: b
Clarification: The circularly polarized light is produced when the phase difference between the two rays is π/2 and the angle of incidence is π/4. In that case, the equation of the polarized light turns out to be x2 + y2 = a2, which is the equation of the circle.
3. Which of the following component is not used during the production of circularly polarized light?
a) Nicol Prism
b) Quarter-wave plate
c) Half-wave plate
d) Light source
Answer: c
Clarification: To produce circularly polarized light, two Nicole prisms are crossed and a quarter-wave plate is placed between them so as to introduce a phase difference between the rays.
4. If the phase difference between two rays is π/2 and the angle of incidence is not equal to π/4, the emergent light is ____________
a) Linearly Polarized
b) Elliptically Polarized
c) Circularly Polarized
d) Non-Polarized
Answer: b
Clarification: In this case, the equation of the emergent light becomes the equation of an ellipse, which is (frac{x^2}{a^2} +frac{y^2}{b^2} = 1). Thus, the emergent light is elliptically polarized and the plane of the ellipse is normal to the direction of propagation.
5. A beam of light is allowed to fall on a Nicol Prism. The prism is rotated. If the light gets completely extinguished twice in one rotation, the nature of the light is __________
a) Unpolarized
b) Plane Polarized
c) Circularly Polarized
d) Elliptically Polarized
Answer: b
Clarification: When a Nicol Prism is rotated, then there would be two stages when the plane polarized light would get completely blocked from passing through the prism, as the arrangement of molecules would be in such a direction that it eliminated the vibration.
6. When a circularly polarized light falls on a quarter wave plate, it changes into a __________
a) Unpolarized light
b) Elliptically Polarized Light
c) Plane Polarized light
d) No change
Answer: c
Clarification: This method is used to distinguish between unpolarized light and a circularly polarized light. When both of them are incident on a quarter-wave plate, a circularly polarized light gets converted into a plane-polarized light while the unpolarized light remains unchanged.
7. A beam of light is incident on a rotating prism. If the intensity of the light changes from a maximum to a minimum (not zero), what is the nature of the incident beam?
a) Unpolarized
b) Plane Polarized
c) Circularly Polarized
d) Elliptically Polarized
Answer: d
Clarification: In this case, the incident beam is elliptically polarized light. The intensity is maximum when the principal plane of the Nicol prism is parallel to the major axis of the ellipse and minimum, when parallel to the minor axis.
8. When a light is analyzed, following observations are made. What is the nature of the light?
a) Plane Polarized
b) Circularly Polarized
c) Elliptically Polarized
d) Partially Polarized
Answer: d
Clarification: When incident on a rotating prism, the intensity varies, with a minimum not equal to zero. Thus, it can be partially polarized or elliptically polarized. After passing through a quarter-wave plate, the intensity still varies with minimum not equal to zero. This means that it is partially polarized.
9. For the production of elliptically polarized light, we need __________
a) Two unpolarized light waves
b) One polarized and one unpolarized light waves
c) Two polarized light waves with same amplitude
d) Two polarized light waves with different amplitude
Answer: d
Clarification: To produce elliptically polarized light waves we need two plane polarized light waves vibrating at right angles to each other having unequal amplitudes with a phase difference of π/2 or a path difference of λ/4.
10. The following apparatus could be used for the production of __________
a) Plane Polarized Wave and Elliptically Polarized Wave
b) Elliptically Polarized Wave and Circularly Polarized Wave
c) Circularly Polarized Wave and Plane Polarized Wave
d) Only Circularly Polarized wave
Answer: b
Clarification: The same apparatus can be used for the production of both elliptically and circularly polarized light, only difference being for the production of circularly polarized light, the light should be incident at an angle of 45o on the quarter-wave plate.