Railway Science (Physics-Light and Optics)

Total Questions: 50

41. Which of the following optical phenomena can explain the flattening of the disk of the Sun at sunrise and sunset? [RRC Group D 26/08/2022 (Afternoon)]

Correct Answer: (d) atmospheric refraction
Solution:

Atmospheric refraction. The deviation of light or other electromagnetic waves from a straight line as it passes through the atmosphere. Dispersion of light - Splitting of white light through a glass prism into its spectrum of colours (in order Violet, Indigo, Blue, Green, Yellow, Orange and Red). Total internal reflection - Complete reflection of a ray of light within a medium. Scattering of light - Change in the direction of propagation of light caused by the large number of particles present in the atmosphere.

42. Solve the following question. [RRC Group D 26/08/2022 (Evening)]

Correct Answer: (c)
Solution: When a ray of light passes through a glass prism the
white light splits to form a band of seven colors on a white screen. The seven colors of the spectrum are Red, Orange, Yellow, Green, Blue, Indigo, and Violet i.e.VIBGYOR.

43. Consider the following statements: [RRC Group D 29/08/2022 (Evening)]

(a) The particles in clouds are larger than the wavelength of different colors in white light coming from the sun.
(b) All colors of white light are scattered by approximately the same amount. Which of the above statements help(s) us to understand the white color of clouds during sunshine?

Correct Answer: (c) Both (a) and (b)
Solution:

Both (a) and (b). The colour of scattered light depends on the size of the scattering particles. Fine particles scatter mainly light of shorter wavelength like blue light, particles of larger size scatter light of longer wavelengths like red color, and particles of very large, the scattered light may appear white. Some examples of scattering - blue color of the sky, White color of clouds, etc.

44. The color of scattered light depends on the size of the scattering particles. Very fine particles scatter mainly the__________light. [RRC Group D 29/08/2022 (Evening)]

Correct Answer: (d) blue
Solution:

Blue. Light is scattered when it falls on various objects. The colour of scattered light depends on the size of the scattering particles.

45. The refractive indices of mediums 1, 2 and 3 are 1.46, 1.65 and 1.31, respectively. If the speed of light in the mediums are V₁ > V₂ > and V₃ , respectively, which of the following relations between them is correct? [RRC Group D 30/08/2022 (Morning)]

Correct Answer: (a) V₃ > V₁ > V₂
Solution:

V₃ > V₁ > V₂. The ratio between the speed of light in vacuum to speed in a medium is the refractive index. The speed of light in a medium depends on the properties of the medium. In electromagnetic waves, the speed of light is dependent on the optical density of the medium. The more optically dense material is, the slower the speed of light. One such indicator of the optical  density of a medium is the refractive index. So,the more the refraction index, the less is the velocity. So, V₃ > V₁ > V₂ is the correct order.

46. The stars are visible______at night. [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (b) above their actual position
Solution:

Above their actual position. At night, the stars seem to be higher in the sky than they actually are. This is due to atmospheric refraction. When the light from a star reaches the earth’s surface, it passes through the different layers of the atmosphere. But our eye will see the star at that position from where light enters it in the straight line direction.

47. An object is placed in front of a concave mirror at a distance thrice its focal length (3f). The image is formed at: [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (b) a point between F and C
Solution:

a point between F and C. The center of curvature (C) is located at 2f. Here the object is placed at a distance 3f. It means that the object is placed beyond C (center of curvature). In this situation, an image is formed between the center of curvature (C) the focus (F). The image thus formed is diminished, real and inverted.

48. An object is placed in front of a concave mirror at a distance twice its focal length (2f). The image is formed at a distance of [RRC Group D 30/08/2022 (Evening)]

Correct Answer: (c) 2f
Solution:

2f. In a Concave mirror if the object is placed at the center of curvature of the mirror Then the image is also formed at the Centre of Curvature and at the same distance. The image formed has the same size as that of the object and it is real and inverted.

49. . Red color is scattered the _________ by fog or smoke because its wavelength is ______ than the wavelength of other color components of white light. [RRC Group D 01/09/2022 (Morning)]

Correct Answer: (c) least, more
Solution:

least, more. Scattering of light- The phenomenon in which light rays deviate from their original path upon striking an obstacle like dust, gas molecules, or water vapors. Rayleigh scattering- The longer the wavelength of radiation, the less it is dispersed.

50. An optical device X has a focal length of - 30 cm. X can be: [RRC Group D 01/09/2022 (Morning)]

Correct Answer: (b) either a concave lens or a concave mirror
Solution:

either a concave lens or a concave mirror. According to the sign convention, the focal length of a concave lens as well as of a concave mirror is always negative. So the given optical device can be either a concave lens or a concave mirror. And focal length of the convex mirror and the convex lens is taken as + (positive).