1. A window which can transmit all the incident light without any reflection is called as ___________
a) Polarized Window
b) Malus Window
c) Brewster Window
d) Non-reflecting window
Explanation: Brewster 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. If the phase difference between two rays is π/2 and the angle of incidence is equal to π/4, the emergent light is __________
a) Linearly Polarized
b) Elliptically Polarized
c) Circularly Polarized
d) Non-Polarized
Explanation: In this case, the equation of the emergent light becomes the equation of a circle, which is x2 + y2 = a2. Thus, the emergent light is elliptically polarized and the plane of the ellipse is normal to the direction of propagation
3. The velocity of light in water is 1.5 X 108 m/s. What is the polarizing angle of incidence?
a) 47.23°
b) 51.02°
c) 53.74°
d) 63.43°
Explanation: Refractive index of water = Speed of light in space/Speed of light in water
= 3/1.5
= 2
Using Brewster’s Law, Angle of incidence = tan-1µ
= tan-12
= 63.43.
4. An electromagnetic beam has an intensity 16 W/m2 and is linearly polarized vertically. What is the intensity of the transmitted beam, if the angle of incidence on the polaroid is 45° with the vertical?
a) 8 Wm-1
b) 12 Wm-1
c) 16 Wm-1
d) 20 Wm-1
Explanation: Here, Io = 16 Wm-2, θ = 45°
Using Malus law, I = Iocos2θ
I = 16 X cos245
I = 8 Wm-1.
5. What should be the thickness of quarter-wave plate for a light of wavelength 5000 Å if µe = 1.553 and µo = 1.544?
a) 1.38 X 10-3 cm
b) 1.43 X 10-3cm
c) 1.53 X 10-3cm
d) 1.63 X 10-3 cm
Explanation: \(t =\frac{λ}{4(μ_E-μ_0)} \)
Λ = 5000 Å = 5000 X 10-8 cm, µe = 1.553 and µo = 1.544
Therefore, t = 5000 Å X 10-8/4 X 0.009
= 1.38 X 10-3 cm.
6. 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°
Explanation: The specific rotation is given by S = 10θ/lC
Here, θ = 13.2°, C = 0.1 g/cc and l = 20 cm
Therefore, S = 10 X 13.2/20 X 0.1
= 66°.
7. Unpolarized light is incident on a plane glass surface. What should be the angle of incidence such that the reflect and refracted rays are perpendicular to each other?
a) 90°
b) 45°
c) 57°
d) 60°
Explanation: Using Brewster’s Law, µ = tanip
In this case, i + r is equal to π/2.
For glass, µ = 1.5
Therefore, ip = tan-1µ = 57°.
8. The second polaroid placed after the ray has been polarized is called as __________
a) Polarizer
b) Analyzer
c) Brewster’s Window
d) Multi Polaroid
Explanation: The second polaroid is placed after the ray has already been polarized to analyze whether the ray is polarized completely or not. Thus, it is called the polarizer
9. Which of the following is a uniaxial crystal?
a) Borax
b) Mica
c) Quartz
d) Selenite
Explanation: 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
10. For a glass surface, the value of polarizing angle is _________
a) 45.7°
b) 52.7°
c) 57.5°
d) 67.8°
Explanation: Polarizing angle is the angle for which the reflected light would be completely plane polarized. For glass, it is 57.5°. Thus, if a light is incident on glass at 57.5° the reflected light would be completely polarized.