Railway Science (Physics-Light and Optics) (Part-III)

Total Questions: 50

1. Which of the following materials CANNOT be used to make a spherical lens? [RRC Group D 16/09/2022 (Afternoon)]

Correct Answer: (c) Wood
Solution:

Wood. Spherical Lens - Transmissive optical device that focuses or disperses a light beam by means of refraction. Convex lens - Lens that converge rays of light that are traveling parallel to its principal axis. Use - Corrective lenses, Magnifying glasses, Cameras, Projectors, Telescopes etc. Concave lens - Diverge a single beam of light when it passes through leading to the formation of upright, diminished and virtual images. Use - Correcting long-sightedness (hypermetropia), Correcting astigmatism.

2. Most ordinary gases do not show dispersion with visible light. This is because the velocities of propagation of waves of different wavelengths of visible light are_______.(Velocity of light in vacuum is c) [RRC Group D 16/09/2022 (Evening)]

Correct Answer: (d) almost the same as c
Solution:

Almost the same as C. Since, the velocity of propagation of waves of various wavelengths of visible light are almost same in most of the ordinary gases therefore, they do not show dispersion on visible light.

3. A reflected ray will follow the same path but in reverse direction when it passes through the pole and_______. [RRC Group D 16/09/2022 (Evening)]

Correct Answer: (c) is perpendicular to the focal plane
Solution:

Is perpendicular to the focal plane. Law of reflection: The angle of incidence = Angle of reflection. The incident ray, reflected ray, and the normal of the system lie in the same plane.

4. Smaller particles scatter the light of ______and ______ colour the most; on the other hand, larger particles scatter the light of ______and _____ colour the most. [RRC Group D 17/09/2022 (Morning)]

Correct Answer: (a) violet, blue; red, orange
Solution:

Violet, blue; red, orange . Scattering of light is the phenomenon in which light rays get deviated from its straight path on striking an obstacle like dust or gas molecules, water vapors and other minute particles. Factors affecting Scattering of light - Size of particle and Wavelength of light.

5. When light is passed through a prism, refraction of light occurs: [RRC Group D 17/09/2022 (Afternoon)]

Correct Answer: (a) two times
Solution:

Two times. As light passes through the prism, it slows and bends, but different wavelengths bend at different angles. This separates light into different wavelengths, forming a rainbow of colors. In this whole process refraction of light occurs two times because when light travels through a glass prism, it is refracted both inside and outside the prism.

6. When we observe the floor of a swimming pool filled with water we notice that the pool looks: [RRC Group D 17/09/2022 (Evening)]

Correct Answer: (d) less deep than it actually is
Solution:

Less deep than it actually is. The rays of light coming from the bottom of the swimming pool are refracted by the water and form a virtual image of the swimming pool. This phenomenon is called the refraction of light. Eyes do not take refraction in account so the swimming pool appears less deep than actual when it is filled with water.

7. If the magnification of an image from a spherical mirror is -1.38, then the nature of the image will be: [RRC Group D 17/09/2022 (Evening)]

Correct Answer: (a) real, inverted and enlarged
Solution:

8. A ray of white light is incident on a refracting surface AB of a glass prism and emerges out of the other refracting surface AC. Consider the following statements: [RRC Group D 18/09/2022 (Morning)]

(A) The angle of refraction at surface AB is different for different colours of white light.
(B) The angle of refraction at the surface AC is different for different colours. Which of the above statements is/are correct?

Correct Answer: (a) Both (A) and (B)
Solution:

Both (A) and (B). Refraction is the bending of light as it passes from one transparent substance into another. The angle of refraction is different for different colors Because different colors have different wavelengths, the speed with which they all bend varies depending on their wavelength. The violet deviates the most, having the shortest wavelength and red deviates the least, having the longest wavelength.

9. If the value of the refractive index increases then: [RRC Group D 18/09/2022 (Evening)]

Correct Answer: (b) deviation in direction of light increases
Solution:

Deviation in direction of light increases. The deviation of light occurs when a beam of light changes route as it travels from one medium to another. The phenomenon of deviation of light rays from their original path,when they pass from one medium to another, is called refraction. As the refractive index of a medium increases, the speed of light in that medium decreases because the speed of light in a medium is inversely proportional to the refractive index of the medium, i.e., n ∝ 1/v

10. The radius of curvature of a spherical mirror is the distance between: [RRC Group D 19/09/2022 (Morning)]

Correct Answer: (b) Centre of curvature and pole
Solution:

Centre of curvature and pole. The focal length of a spherical mirror is the distance between the pole of the mirror and the focus of the mirror on the principal axis. Rays parallel to the principal axis converge on the focus (for a concave mirror) or appear to diverge from the focus (for a convex mirror). Centre of curvature = 2 × focal lengths.