Engineering Physics Multiple Choice Questions on “Polarization”.
1. A window which can transmit all the incident light without any reflection is called ___________
a) Polarized Window
b) Malus Window
c) Brewster Window
d) Non-reflecting window
Answer: c
Clarification: Brewster’s window is the practical use of Brewster law. When light is incident on a clean glass plate, most of the incident light (>> 92%) is transmitted while a small fraction is reflected.
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. Sound waves can be polarized.
a) True
b) False
Answer: b
Clarification: Longitudinal waves cannot be polarized as their direction is the same as its vibration. Thus, it’s intensity will not change as it passes through a rotating analyzer.
4. Which of the following is a uniaxial crystal?
a) Borax
b) Mica
c) Quartz
d) Selenite
Answer: c
Clarification: Uniaxial crystals are those in which there is only one optic axis. Calcite, quartz, ice are a few examples. Borax, mica, and selenite are biaxial crystals which have two optic axes.
5. 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.
6. The velocity of light in water is 2.2 X 108 m/s. What is the polarizing angle of incidence?
a) 47.23
b) 51.02
c) 53.74
d) 65.36
Answer: c
Clarification: Refractive index of water = Speed of light in space/Speed of light in water
= 3/2.2
= 1.3636
Using Brewster’s Law, Angle of incidence = tan-1μ
= tan-11.3636
= 53.74.
7. An electromagnetic beam has an intensity 28 W/m2 and is linearly polarized vertically. What is the intensity of the transmitted beam, if the angle of incidence on the polaroid is 45o with the vertical?
a) 10 Wm-1
b) 12 Wm-1
c) 14 Wm-1
d) 16 Wm-1
Answer: c
Clarification: Here, Io = 28 Wm-2, θ = 45
Using Malus law, I = Iocos2θ
I = 28 X cos245
I = 14 Wm-1.
8. What should be the thickness of quarter-wave plate for a light of wavelength 5890 Å if µe = 1.553 and µo = 1.544?
a) 1.33 X 10-3 cm
b) 1.43 X 10-3 cm
c) 1.53 X 10-3 cm
d) 1.63 X 10-3 cm
Answer: d
Clarification: t = (frac{lambda}{4(μ_E-μ_0)})
Λ = 5890 Å = 5890 X 10-8 cm, µe = 1.553 and µo = 1.544
Therefore, t = 5890a X 10-8/4 X 0.009
= 1.63 X 10-3 cm.
9. A tube of length 20cm containing a 10% sugar solution rotates the plane of polarization by 13.2°. What is the specific rotation of sugar solution?
a) 66°
b) 55
c) 44
d) 33
