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31. Which one of the following is not a luminous object ?
A. Sun
B. Electric lamp
C. Candle
D. Moon
ANSWER:D
SOLUTION :The moon is not a luminous object because it doesn’t produce its own light, but instead reflects light from the sun. A luminous object is one that produces its own light.
32. Near – sightedness is humans is called ________.
A. Myopia
B. Hypermetropia
C. Cataract
D. Presbyopia
ANSWER:A
SOLUTION:The medical term for nearsightedness is myopia. Myopia happens when the shape of the eye — or the shape of certain parts of the eye — causes light rays to bend or refract.
33. Light is a transverse wave, which of the only event proving this ?
A. Dispersion of light
B. Interference
C. Diffusion
D. Polarization
ANSWER:D
SOLUTION:Polarization of light proved that light is a transverse wave.
34. What is the absolute refractive index of air ?
A. 1.03
B. 1.00003
C. 1.003
D. 1.0003
ANSWER:D
SOLUTION:The absolute refractive index of air is approximately 1.0003 at sea level under standard conditions. It’s a dimensionless number that indicates how much light bends when entering a material.
35. To an astronaut in space, the sky will appear to be ________.
A. Violet
B. Red
C. Blue
D. Black
ANSWER:D
SOLUTION:To an astronaut, the sky looks dark and black instead of blue because there is no atmosphere containing air in the outer space to scatter sunlight. So, there is no scattered light to reach our eyes in outer space, therefore the sky looks dark and black there.
36. Who can be held responsible for the fact that the sun is visible 2 minutes before the actual sunrise and about 2 minutes after the actual sunset?
A. Atmospheric reflection
B. Internal reflection produced in atmospheric water droplets
C. Sunlight spreads by small drops of water present in the atmosphere
D. Atmospheric refraction
ANSWER:D
SOLUTION : The phenomenon of atmospheric refraction is responsible for the sun being visible about two minutes before sunrise and two minutes after sunset.
37. The process of glare resulting from a collision caused by a collision with particles floating in a fluid of light is called ______.
A. Raman effect
B. Tyndall effect
C. Snail effect
D. Huygen’s effect
ANSWER:B
SOLUTION:The Tyndall effect is the phenomenon in which the particles in a colloid scatter the beams of light that are directed at them. This effect is exhibited by all colloidal solutions and some very fine suspensions. Therefore, it can be used to verify if a given solution is a colloid.
38. Light enters the eye from __________.
A. Ciliary Muscle
B. Cornea
C. Iris
D. Lens
ANSWER:B
SOLUTION: The light enters our eye through the transparent cornea, passes through the lens, and is focused on the retina. The retina is sensitive to light and sends images to our brain through the optic nerve. The cornea is the part of our eye that covers the iris and the pupil and lets light enter.
39. A water tank appears shallower when it is viewed from top due to _______.
A. Rectilinear propagation of light
B. Reflection
C. Total internal reflection
D. Refraction
ANSWER:D
SOLUTION: A water tank appears shallower when viewed from the top due to refraction of light.
40. Due to atmospheric refraction,sunrise and sunset can be delayed by about _______.
A. 3 minutes
B. 2 minutes
C. 4 minutes
D. 1 minute
ANSWER:B
SOLUTION: To sum up, due to refraction we see the sun rise about two minutes before it’s actually there and during sunset we see it for around two minutes more, even though it has already moved from that position.