10. Light : Reflection and Refraction

SEBA Class 10 Science Chapter 10. Light : Reflection and Refraction

Chapter 10. Light : Reflection and Refraction

Class 10 Science Chapter 10 Light : Reflection and Refraction Multiple Choice Questions and Answers :

Question : Which one of the following materials cannot be used to make a lens?
(a) Water (b) Glass (c) Plastic (d) Clay

Answer : (d) Clay
Question : The image formed by a concave mirror is observed to be virtual, erect and larger
than the object. Where should be the position of the object?
(a) Between the principal focus and the centre of curvature
(b) At the centre of curvature
(c) Beyond the centre of curvature
(d) Between the pole of the mirror and its principal focus.

Answer : (d) Between the pole of the mirror and its principal focus.
Question : Where should an object be placed in front of a convex lens to get a real image of the
size of the object?
(a) At the principal focus of the lens
(b) At twice the focal length
(c) At infinity
(d) Between the optical centre of the lens and its principal focus.

Answer : (b) At twice the focal length .
Question : A spherical mirror and a thin spherical lens have each a focal length of –15 cm. The
mirror and the lens are likely to be
(a) both concave.
(b) both convex.

Answer : (a) both concave.
Question : No matter how far you stand from a mirror, your image appears erect. The mirror
is likely to be
(a) plane.
(b) concave.
(c) convex.
(d) either plane or convex.

Answer : (d) either plane or convex.
Question : Which of the following lenses would you prefer to use while reading small letters
found in a dictionary?
(a) A convex lens of focal length 50 cm.
(b) A concave lens of focal length 50 cm.
(c) A convex lens of focal length 5 cm.
(d) A concave lens of focal length 5 cm.

Answer : (c) A convex lens of focal length 5 cm.

Question: The focal length of a lens is 1 metre. Its power is : [SEBA 2023]

(a) 0.5 D

(b) 1 D

(d) 2 D

Answer : (b) 1D

[ Here, metre

We have, ]

Question : Image formed by a concave mirror is : [SEBA 2023]

(a) real and diminished (b) real and enlarged (c) virtual and enlarged (d) virtual and diminished

Answer : (b) real and enlarged .

Question: If the refractive index of the glass is 1.5, then speed of light in glass is : [SEBA 2023]

(a) m/s

(b) m/s

(d) m/s

Answer : (a) m/s

[ Here, and

We have,

]

Question : The mirror is used as rear view in vehicles . [SEBA 2023]

Answer : Convex .

[Convex mirrors are commonly used as rear-view (wing) mirrors in vehicles.]

Question : Which of the following can make a parallel beam of light when light from a point source is incident on it?

(a) Concave mirror as well as convex lens

(b) Convex mirror as well as concave lens

(d) Concave mirror as well as concave lens

Answer : (a) Concave mirror as well as convex lens.

[ Both a concave mirror and a convex lens have the ability to converge parallel rays of light to a point focus. In the case of a concave mirror, parallel rays converge after reflection, while in the case of a convex lens, parallel rays converge after refraction. Therefore, both a concave mirror and a convex lens can create a parallel beam of light when light from a point source is incident on them.]

Question : A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is

(a) – 30 cm

(b) – 20 cm

(d) – 60 cm

Answer : (b) – 20 cm

[ Here, , ,

We have ,

Using mirror formula , we have

]

Question : Under which of the following conditions a concave mirror can form an image larger than the actual object?

(a) When the object is kept at a distance equal to its radius of curvature

(b) When object is kept at a distance less than its focal length

(d) When object is kept at a distance greater than its radius of curvature

Answer : (c) When the object is placed between the focus and the centre of curvature.

[ In a concave mirror, when an object is located between the focus (F) and the centre of curvature (C), the mirror forms a magnified and virtual image that is larger than the actual object. This is a specific case where the concave mirror exhibits magnification greater than one.]

Question : Figure 10.1 shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is

(a)

(b)

(c)

(d)

Answer : (a)

[ Refractive index of the medium B relative to medium A ]

Question : A light ray enters from medium A to medium B as shown in Figure 10.2. The refractive index of medium B relative to A will be

(a) greater than unity

(b) less than unity

(d) zero

Answer : (a) greater than unity

Question : Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the Figure10.3. Which of the following could be inside the box?

(a) A rectangular glass slab

(b) A convex lens

(d) A prism

Answer : (a) A rectangular glass slab

Question : 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 the Figure 10.4. Which of the following could be inside the box?

(a) Concave lens

(b) Rectangular glass slab

(d) Convex lens

Answer : (d) Convex lens

Question : 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

(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

[ Here,

We have,

]

Question : Magnification produced by a rear view mirror fitted in vehicles

(a) is less than one

(b) is more than 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 .

[ The magnification produced by a rear-view mirror fitted in vehicles is less than one. The purpose of a rear-view mirror in vehicles is to provide a wider field of view to the driver. To achieve this, the mirror typically forms an upright and diminished image of the objects behind the vehicle. As the image is diminished, the magnification (ratio of the image height to the object height) is less than one. ]

Question : 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

(d) more than 30 cm in front of the mirror

Answer : (d) more than 30 cm in front of the mirror.

[Here,

We have, ]

Question : A full length image of a distant tall building can definitely be seen by using

(a) a concave mirror

(b) a convex mirror

(d) both concave as well as plane mirror

Answer : (b) a convex mirror.

[ A convex mirror, due to its outward curved surface, diverges light rays. When you look at a distant tall building in a convex mirror, it forms a diminished and virtual image that allows you to see the full length of the building. This is why convex mirrors are commonly used as rear-view mirrors in vehicles and in situations where a wide field of view is required. In contrast, concave mirrors would produce a magnified and virtual image, and plane mirrors would not provide the wide field of view needed to see the full length of a distant tall building. ]

Question : In torches, search lights 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

(d) at the centre of curvature of the reflector

Answer : (b) very near to the focus of the reflector.

[ This positioning helps in producing parallel or nearly parallel rays of light after reflection, which is useful for applications where a strong, focused beam of light is required.]

Question : The laws of reflection hold good for

(a) plane mirror only

(b) concave mirror only

(d) all mirrors irrespective of their shape

Answer : (d) all mirrors irrespective of their shape.

[ The laws of reflection state that the angle of incidence is equal to the angle of reflection, and these laws hold true for all types of mirrors, including plane mirrors, concave mirrors, and convex mirrors. So, the correct statement is that the laws of reflection are applicable to all mirrors, regardless of their shape.]

Question : 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 10.5. Which one of them is correct?

(a) A (b) B (c) C (d) D

Answer : (b) B

Question : 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

(d) Glycerine

Answer : (d) Glycerine

[The amount by which light bends as it passes from one medium to another is determined by the refractive index of the media. The refractive index is a measure of how much the speed of light changes in a particular medium.

Glycerine tends to have a higher refractive index compared to the others. Therefore, a ray of light incident obliquely at the same angle would bend the most in glycerine. ]

Question : Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure 10.6 ?

(a) Fig. A

(b) Fig. B

(d) Fig. D

Answer : (d) Fig. D

Question : Which of the following ray diagrams is correct for the ray of light incident on a lens shown in Fig. 10.7?

(a) Fig. A. (b) Fig. B. (c) Fig. C. (d) Fig. D.

Answer : (a) Fig. A

Question : 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

(d) Convex, plane and concave

Answer : (c) Concave, plane, and convex.

[ This pattern of image sizes (head bigger, middle portion the same size, and legs smaller) suggests that the mirror has a combination of concave, plane (flat), and convex surfaces from top to bottom. The concave mirror would enlarge the head, the flat or plane section would maintain the size, and the convex mirror would reduce the size, creating the observed effect. ]

Question : 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

(d) Concave mirror, convex mirror, concave lens and convex lens

Answer : (d) Concave mirror, convex mirror, concave lens, and convex lens.

[ In the case of concave mirrors and convex lenses, when an object is placed at infinity, the image formed is highly diminished and point-sized. For convex mirrors, the image is also diminished and point-sized when the object is at infinity. Concave lenses can also produce a highly diminished image of an object at infinity. Therefore, all the given options (concave mirror, convex mirror, concave lens, and convex lens) can exhibit this behavior.]