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

Total Questions: 50

21. A ray of light is incident on a refracting surface AB of a glass prism and emerges out of the other refracting surface AC. [RRC Group D 09/09/2022 (Morning)]

Consider the following statements:
(A) The angle of refraction at surface AB is more than the angle of incidence. (B) The angle of refraction at the surface AC is less than the angle of incidence. Which of the above statements is/are correct?

Correct Answer: (c) Neither (A) nor (B)
Solution:

Neither (a) nor (B). If a ray of light is incident on a refracting surface AB of a glass prism and emerges out of the other refracting surface AC.Then the angle of refraction at surface AB is not more than the angle of incidence and the angle of refraction at the surface AC is not less than the angle of incidence. So, both the given statements are incorrect.

22. The focal length of a convex mirror is: [RRC Group D 09/09/2022 (Afternoon)]

Correct Answer: (d) positive
Solution:

Positive. The focal length - Defined as the distance from the primary focus to its pole. For a converging or concave mirror, the focal length is always negative. The focal length of a convex mirror is half of its radius of curvature.

23. When blue and orange lights, which are parallel to each other, are passed through prism then: [RRC Group D 09/09/2022 (Evening)]

Correct Answer: (a) blue ray will bend more
Solution:

blue ray will bend more. When yellow, orange and blue color light is passed through the prism, the blue color light will bend the most as its wavelength is least in comparison to other colors. Refraction of Light Through Prism: When light travels from one medium to another, the speed of its propagation changes, as a result, it 'bends' or is 'refracted'. It is refracted towards the base of the triangle.

24. A ray of light is incident on a refracting surface AB of glass prism, kept in air, and emerges out of the other refracting surface AC. Consider the following statements: [RRC Group D 12/09/2022 (Morning)]

Correct Answer: (c) Only (A)
Solution:

Only (A). Refraction is the bending of light when it goes from one medium to another so, when a ray of light passes through a glass prism, refraction of light occurs both, when it enters the prism as well as when it leaves the prism. Since the refracting surfaces are not parallel, therefore, the emergent ray and incident ray are not parallel to one another. In this case the ray of light is deviated on passing through the prism. Examples of atmospheric refraction of light : Twinkling of stars, Stars appear higher than they are, early sunrise and delayed sunset

25. The random wavering of objects seen through a turbulent stream of hot air rising above a fire can be explained using: [RRC Group D 12/09/2022 (Morning)]

Correct Answer: (d) atmospheric refraction
Solution:

Atmospheric refraction. Examples : Twinkling of stars, Apparent higher position of a star, Early sunrise and delayed sunset. Flattened appearance of sun during sunrise and sunset .

26. The focal length of a concave mirror is: [RRC Group D 12/09/2022 (Morning)]

Correct Answer: (c) always negative
Solution:

Always negative. A concave mirror is a type of spherical mirror in which the reflecting surface is the inner curved surface of the sphere. Concave mirrors form both real and virtual images. Eg- the mirrors used in automobile headlights, reflecting telescopes, torch lights, etc. The focal length of an optical system is a measure of how strongly the system converges or diverges light

27. Which of the following points always lie(s) on the principal axis of a spherical mirror? [RRC Group D 12/09/2022 (Afternoon)]

Correct Answer: (d) Both (i) and (iii)
Solution:

Both (i) and (iii). Spherical mirror - A mirror that has the shape of a piece cut out of a spherical surface. Types - concave mirror and convex mirror.

28. During dispersion of light through a triangular prism white light will split into______ bands of colour. [RRC Group D 12/09/2022 (Afternoon)]

Correct Answer: (c) seven
Solution:

Seven. Prism - A transparent solid body that has three rectangular lateral surfaces and two triangular faces that are inclined at an angle. Dispersion - Separation of white light into different colors when the light is passed through the prism depending on the wavelength of the light.

29. An object is placed at a distance of 30 cm in front of a convex mirror of focal length 10 cm, on its principal axis. Its image is formed at: [RRC Group D 12/09/2022 (Evening)]

Correct Answer: (b) a point between 0 cm and 10 cm
Solution:

A point between 0 cm and 10 cm. In the case of a convex mirror no matter where the object is placed (except for infinity) the image is always formed between the pole and the focal length of the mirror.

30. When light travels from one medium to another medium then: [RRC Group D 12/09/2022 (Evening)]

Correct Answer: (a) incident ray, normal at the point of incidence and refracted ray all are in the same plane
Solution:

Second Law of refraction : The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is also known as Snell’s law of refraction. Refraction - Bending of light as it passes from one transparent substance into another. This bending by refraction makes it possible for us to have lenses, magnifying glasses, prisms and rainbows.