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

Total Questions: 50

31. A simple magnifying glass consists of: [RRB Group D 28/09/2018 (Evening)]

Correct Answer: (d) Convex lens of short focal length
Solution:

Convex lens of short focal length. A simple magnifier is a converging lens and produces a magnified virtual image of an object located within the lens’s focal length. The simple magnifier is a convex lens used to produce an enlarged image of an object on the retina.

32. In what does light travel at the highest speed? [RRB Group D 01/10/2018 (Morning)]

Correct Answer: (a) vacuum
Solution:

Vacuum is the least dense medium with no obstruction to the path of light. Its refractive index is equal to unity, hence, the speed of light is maximum in a vacuum. The higher the refractive index of the medium, the lower is the speed of light.

33. When light travels from a denser medium to a rarer medium, what is the effect on its speed ? [RRB Group D 01/10/2018 (Evening)]

Correct Answer: (a) Increases
Solution:

Increases. The refraction of light is the phenomenon of bending or changing the direction of light rays when it passes from one medium to another

34. The absolute refractive index of any medium is always: [RRB Group D 03/10/2018 (Morning)]

Correct Answer: (a) more than one
Solution:

more than one. Refractive index (n): Measure of the bending of a ray of light when passing from one medium into another (n = speed of light in vacuum / speed of light in medium). It has no dimension or units. Optical Materials and their Refractive index (n): Vacuum (1), Air (1.0003), Water (1.33), Glass (1.5), Diamond (2.42).

35. When light travels from a rarer medium to a denser medium, it_______. [RRB Group D 03/10/2018 (Afternoon)]

Correct Answer: (c) speeds down
Solution:

Speeds down. When light passes through any medium, it interacts with the atoms and molecules present. This interaction causes the light to slow down due to the energy transfer between the light and the medium.

36. ___________ Lenses are used by people suffering from nearsightedness (myopia). [RRB Group D 04/10/2018 (Afternoon)]

Correct Answer: (c) concave
Solution:

Concave lens: Deviates light beams, creating a diminished, upright, virtual image. Cylindrical lens: Used for astigmatism correction. Convex lens: Use for treating hypermetropia (farsightedness). Bifocal lens: Used for treating presbyopia (combination of myopia and hypermetropia).

37. _______ mirror produces an image that is always virtual, erect and the same size as that of the object. [RRB Group D 05/10/2018 (Morning)]

Correct Answer: (c) Plane
Solution:

Plane. Uses - looking glass, solar cookers, Torch Lights. A convex mirror always produces a virtual, erect, and diminished image of an object. A concave mirror can produce either a real or virtual image, depending on the distance of the object from the mirror. A plano-convex mirror is a type of mirror that has one side that is flat and the other side that is convex. The image produced by a plano-convex mirror is similar to the image produced by a convex mirror.

38. A ray of light passing through the _______ of a lens will emerge without any deviation. [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (d) optical center
Solution:

optical center. Principal focus: It is a point (on the principal axis) where parallel incident rays meet after reflecting (in mirrors) or refracting (in lenses). Principal axis : It is a straight line that passes through the pole and centre of curvature of a spherical mirror or lens. Focal length is the distance between the optical center of lens and Principal focus.

39. _______ is also called a converging mirror. [RRB Group D 10/10/2018 (Morning)]

Correct Answer: (b) Concave mirror
Solution:

Concave mirror. It is a mirror with a reflecting surface that curves inward like the interior of a sphere. When light rays parallel to the principal axis strike a concave mirror, they converge at a point in front of the mirror after reflection. This point is called the focal point, and the distance from the mirror to the focal point is called the focal length.

40. ________ is also called a diverging mirror. [RRB Group D 10/10/2018 (Evening)]

Correct Answer: (b) convex mirror
Solution:

Convex mirror. It is a spherical mirror whose reflecting surface is curved outwards. Nature of Image - Virtual, Erect and Diminished. Uses of convex mirrors - Side-view mirrors on vehicles like buses, trucks, and vans; they are installed in stores, warehouses, and parking lots to provide a wide-angle view of areas.