1. 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
Explanation: 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.
2. 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
Explanation: Here, Io = 28 Wm-2, θ = 45
Using Malus law, I = Iocos2θ
I = 28 X cos245
I = 14 Wm-1.
3. 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
Explanation: 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.
4. 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°.
5. 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°.
6. A plate which induces the desired amount of phase difference between two rays is known as ___________
a) Polaroid
b) Phasor plates
c) Retardation Plates
d) Quartz plates
Explanation: Sometimes, it is required to induce a certain phase difference between E-ray and O-ray. For that, a plate with a specific thickness is chosen to induce that phase difference. This plate is known as the retardation plate as it retards the motion of one of the rays.
7. The inability of a lens to form a white image of a white object is known as ________
a) Spherical Aberration
b) Chromatic Aberration
c) Monochromatic Aberration
d) Coma
Explanation: If a lens forms colored images of an object with white light, it is known as chromatic aberration. Because since that the refractive index of the material of the lens is different for different wavelengths of light.
8. What is the ratio of the focal lengths of the two Plano-convex lenses in Huygens’s Eyepiece?
a) 2:1
b) 3:1
c) 3:2
d) 4:3
Explanation: The focal lengths of the two Plano-convex lenses in Huygens’s Eyepiece are in the ration 3:1(3f and f) and the distance between them is equal to 2f. The focal length and positions of the two lenses are such that the eyepiece is achromatic and free from spherical aberration.
9. In which of the following instruments, the objective has a large focal length and a very large eyepiece?
a) A simple microscope
b) A Compound microscope
c) Telescope
d) Interferometer
Explanation: In telescopes, it is desired to provide angular magnification of distant objects. A very large focal length and the even larger eyepiece is used so that the light from a distant object enters the objective and the image formed is clear.
10. X is an optical defect due to which a comet-like image is formed instead of a point image. X is ___________
a) Coma
b) Astigmatism
c) Curvature
d) Distortion
Explanation: Coma is a type of monochromatic aberration. In this, a comet-like image is formed instead of a point image, of a point object situated away from the lens. It can be reduced by using the aplanatic lens.