Railway Science (Physics-Light and Optics)

Total Questions: 50

11. The apparent position of a star keeps on changing slightly because: [RRC Group D 18/08/2022 (Afternoon)]

Correct Answer: (b) the physical conditions of the atmosphere keep changing
Solution:The twinkling of a star is due to atmospheric refraction of starlight. The temperature and density of the different layers of the atmosphere keep varying. Since the atmosphere bends the starlight towards normal, the apparent position of the star appears to be slightly different from its actual position. Stellar parallax is the apparent shift of position of any nearby star against the background of distant stars.

12. The magnification produced by a spherical mirror is -0.5. The image formed by the mirror is: [RRC Group D 18/08/2022 (Evening)]

Correct Answer: (b) real, inverted and diminished
Solution:Real, inverted and diminished. If the magnification produced by the spherical mirror is -0.5, then the image will be real, inverted, and diminished and the mirror is a converging mirror or Concave mirror. The Object's Position is beyond the Centre of Curvature, and the Image's location is between the Center of Curvature and the Focal point.

The Magnification =Β  π»π‘’π‘–π‘”β„Žπ‘‘ π‘œπ‘“ π‘‘β„Žπ‘’ πΌπ‘šπ‘Žπ‘”π‘’/π»π‘’π‘–π‘”β„Žπ‘‘ π‘œπ‘“ π‘‘β„Žπ‘’ 𝑂𝑏𝑗𝑒𝑐t .

13. Which of the following line(s) act as a normal to a spherical mirror? [RRC Group D 18/08/2022 (Evening)]

(i) Line joining the pole and center of curvature
(ii) Line joining the center of curvature and point of incidence
(iii) Line joining focus and point of incidence

Correct Answer: (a) Both (i) and (ii)
Solution:Both (i) and (ii). In a spherical mirror, normal drawn on any point on the spherical mirror passes through the center of curvature. So, the line passing joining the center of curvature from any point either pole or point of incidence is normal to the spherical mirror. Two types of spherical mirror - concave mirror (converging mirrors because light converges at a certain point) and convex mirror (diverging mirror because diverging the light ).

14. Planets do not twinkle because [RRC Group D 18/08/2022 (Evening)]

Correct Answer: (c) they act as extended source of light
Solution:Planets do not twinkle because they are nearer to earth and hence earth receives a greater amount of light and, therefore minor variations in the intensity are not noticeable. Twinkling of stars is due to atmospheric refraction.

15. A ray of light AB is incident on a convex mirror as shown in figure. What will be its reflection angle? [RRC Group D 22/08/2022 (Afternoon)]

Correct Answer: (b) 0Β°
Solution:0Β° . As the ray of light passes through the centre of curvature of a convex mirror it strikes the mirror along the normal (i.e. it incidences on to the mirror at 90 degree and 0 degree with normal). Hence the incident ray coincides with the normal. Therefore, the angle of reflection is 0 degree.

16. For a ray of light undergoing refraction through a triangular glass prism, the angle of deviation is the angle between [RRC Group D 22/08/2022 (Afternoon)]

Correct Answer: (b) the incident ray and the emergent ray
Solution:

Incident ray and the emergent ray. It is produced by a light ray depending on 4 factors: incident angle, the material of the prism, the wavelength of light used, the angle of the prism. Angle of refraction - the angle between the refracted ray and normal at the point of incidence.

17. The component of white light that deviates the most on passing through a glass prism is: [RRC Group D 22/08/2022 (Evening)]

Correct Answer: (c) violet
Solution:

Violet. Dispersion of light: When a white light is passed through a prism it splits into its seven constituent colors (VIBGYOR). The Red color ( wavelength-700 nm) deviates least and Violet color (wavelength-400nm) deviates most because its wavelength is shortest among other colors.

18. A spherical mirror converges a beam of light, at a given point on the principal axis. Which of the following statement(s) about the mirror is/are true? [RRC Group D 22/08/2022 (Evening)]

(A) The mirror used is concave
(B) The mirror has positive focal length
(C) The point of convergence is the principal focus of the mirror

 

Correct Answer: (d) Both (A) and (C)
Solution:

Both (a) and (c).

If a parallel beam of light is incident on a
concave mirror, it converges the beam to
a point called focus. The focal length of
the mirror is equal to half of the radius of
curvature of the spherical mirror and is
given by the relation: f = 𝑅/2
where, f is the focal length of the
spherical mirror and, R is the Radius of
Curvature of the spherical mirror.

19. P, Q, R and S are four points on the surface of a concave mirror as shown in the figure. If r₁, rβ‚‚, r₃, and rβ‚„ are the distance of centre of curvature from points P, Q, R and S respectively, then the correct relation between r₁, rβ‚‚, r₃, and rβ‚„ is: [RRC Group D 23/08/2022 (Morning)]

Correct Answer: (b) r₁ = rβ‚‚ = r₃ = rβ‚„
Solution:

r₁ = rβ‚‚ = r₃ = rβ‚„. Spherical mirror - Has a consistent curve and a constant radius of curvature, images formed by can either be real or virtual. Types - Concave Mirror (inner side of the spherical mirror is reflecting) and Convex Mirror (outer side of the spherical mirror is reflecting).

20. Lemons placed inside a beaker filled with water appear relatively larger in size due to: [RRC Group D 23/08/2022 (Morning)]

Correct Answer: (b) refraction of light
Solution:

Refraction of Light: The bending of the ray of light passing from one medium to the other medium. Refraction is used in telescopes, microscopes, peepholes of house doors, cameras, movie projectors, magnifying glasses, etc. Reflection of light : Returning light from the surface of an object when the light is incident on it. Examples: Reflection by a plane mirror or spherical mirror. Scattering of light: Bouncing off of the light in a random direction by the atoms or molecules of the medium through which it is traveling. Examples : Red color of sun at sunrise and sunset, Blue color of sky, Red color used as danger signal. Dispersion of light : Spreading of white light into its constituent colors. Example - Rainbow.