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31 Aug 2021: PIB Summary & Analysis

TABLE OF CONTENTS 1. BIMSTEC 2. Naval Anti-Drone System (NADS) 3. Indian Navy’s Maiden Exercise with Algerian Navy 4. 'New Central Sector... View Article

Refractive index of diamond with respect to glass is 1.6 and the absolute refractive index of glass is 1.5. Find out the absolute refractive index of diamond.

Answer: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for the light of a given colour... View Article

How is the refractive index of a medium related to the speed of light? Obtain an expression for the refractive index of a medium with respect to another in terms of speed of light in these two media?

Answer: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, for the light of a given colour... View Article

Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram.

Answer: The opposite faces of a glass slab are parallel. As a result, the angle of refraction at the first interface becomes the angle of... View Article

Identify the device used as a spherical mirror or lens in the following cases, when the image formed is virtual and erect in each case. (a) Object is placed between the device and its focus, an image formed is enlarged and behind it. (b) Object is placed between the focus and device, an image formed is enlarged and on the same side as that of the object. (c) Object is placed between infinity and device, an image formed is diminished and between focus and optical centre on the same side as that of the object. (d) Object is placed between infinity and device, image formed is diminished and between pole and focus, behind it.

Answer: (a) Concave mirror (b) Convex lens (c) Concave lens (d) Convex mirror A convex lens is a lens with an outward curve. The... View Article

In which of the following, the image of an object placed at infinity will be highly diminished and point sized? (a) Concave mirror only (b) Convex mirror only (c) Convex lens only (d) Concave mirror, convex mirror, concave lens and convex lens

Answer: (d) Concave mirror, convex mirror, concave lens and convex lens A highly diminished picture is generated at the focus when rays of... View Article

A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top. (a) Plane, convex and concave (b) Convex, concave and plane (c) Concave, plane and convex (d) Convex, plane and concave

Answer: (c) Concave, plane and convex Because the head is larger, the mirror must be concave. Here, a concave mirror creates an enlarged and... View Article

Which of the following ray diagrams is correct for the ray of light incident on a lens shown in Figure? (a) Fig. A. (b) Fig. B. (c) Fig. C. (d) Fig. D.

Answer: (a) Fig. A. In the convex lens, the incident ray passing through F goes parallel to the principal axis after refraction. A convex... View Article

Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure? (a) Fig. A (b) Fig. B (c) Fig. C (d) Fig. D

Answer: (d) Fig. D In the case of a concave mirror, an incident ray is parallel to the principal axis passes through F after reflection.... View Article

You are given water, mustard oil, glycerine and kerosene. In which of these media a ray of light incident obliquely at same angle would bend the most? (a) Kerosene (b) Water (c) Mustard oil (d) Glycerine

Answer: (d) Glycerine The refractive index is the ratio of the sine of the angle of incidence to the sine of the angle of refraction.... View Article

The path of a ray of light coming from air passing through a rectangular glass slab traced by four students are shown as A, B, C and D in Figure. Which one of them is correct? (a) A (b) B (c) C (d) D

Answer: (b) B Light bends towards normal when it passes from air to glass. Light bends away from normal when it passes from glass to air. This... View Article

The laws of reflection hold good for (a) plane mirror only (b) concave mirror only (c) convex mirror only (d) all mirrors irrespective of their shape

Answer: (d) all mirrors irrespective of their shape The laws of reflection apply to all reflecting surfaces, regardless of whether they are... View Article

In torches, searchlights and headlights of vehicles the bulb is placed (a) between the pole and the focus of the reflector (b) very near to the focus of the reflector (c) between the focus and centre of curvature of the reflector (d) at the centre of curvature of the reflector

Answer: (b) very near to the focus of the reflector To create a parallel beam of light through which we can see further, the bulb in torches,... View Article

A full-length image of a distant tall building can definitely be seen by using (a) a concave mirror (b) a convex mirror (c) a plane mirror (d) both concave as well as plane mirror

Answer: (b) a convex mirror A convex mirror, regardless of the object's position, creates a virtual and smaller image. Using a convex mirror,... View Article

Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object? (a) 15 cm in front of the mirror (b) 30 cm in front of the mirror (c) between 15 cm and 30 cm in front of the mirror (d) more than 30 cm in front of the mirror

Answer: (b) 30 cm in front of the mirror When the object distance equals the radius of curvature, i.e. twice the focal length, the image size... View Article

Magnification produced by a rearview mirror fitted in vehicles (a) is less than one (b) is more than one (c) is equal to one (d) can be more than or less than one depending upon the position of the object in front of it

Answer: (a) is less than one Convex mirrors are used in vehicles for rearview due to their wide field of view. And the convex mirror forms a... View Article

Which of the following statements is true? (a) A convex lens has 4 dioptre power having a focal length 0.25 m (b) A convex lens has –4 dioptre power having a focal length 0.25 m (c) A concave lens has 4 dioptre power having a focal length 0.25 m (d) A concave lens has –4 dioptre power having a focal length 0.25 m

Answer: (a) A convex lens has 4 dioptre power having a focal length 0.25 m 1 dioptre of power of a lens is described as the unit of... View Article

A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in Figure. Which of the following could be inside the box? (a) Concave lens (b) Rectangular glass slab (c) Prism (d) Convex lens

Answer: (d) Convex lens A convex lens is a lens with an outward curve. The thickness at the centre of a convex lens is more than the... View Article

Beams of light are incident through the holes A and B and emerge out of the box through the holes C and D respectively as shown in the Figure. Which of the following could be inside the box? (a) A rectangular glass slab (b) A convex lens (c) A concave lens (d) A prism

Answer: (a) A rectangular glass slab A rectangular glass slab might be inside the box since lateral displacement occurs in parallel rays. The... View Article

A light ray enters from medium A to medium B as shown in Figure. The refractive index of medium B relative to A will be (a) greater than unity (b) less than unity (c) equal to unity (d) zero

Answer: (a) greater than unity The bending of a wave when it enters a medium with a different speed is known as refraction. When the light... View Article

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