# Samacheer Kalvi Class 10 Optics Questions and Answers - 1

Question: 1

A small bulb is placed at the principal focus of a convex lens. When the bulb is switched on, the lens will produce

(A) A convergent beam of light

(B) A parallel beam of light

(C) A coloured beam of light

(D) A divergent beam of light

Ans: B

A parallel beam of light

Question: 2

Which of the following lens would you prefer to use while reading small letters found in a dictionary?

(A) A concave lens of focal length 5 cm

(B) A convex lens of focal length 5 cm

(C) A concave lens of focal length 10 cm

(D) A convex lens of focal length 10 cm

Ans: B

A convex lens of focal length 5 cm

Question: 3

Magnification of a convex lens is

(A) Zero

(B) Positive

(C) Negative

(D) Either positive or negative

Ans: D

Either positive or negative

Question: 4

Power of a lens is -4D, then its focal length is

(A) -0.25 m

(B) -2.5 m

(C) -40 m

(D) 4 m

Ans: A

-0.25 m

Question: 5

Where should an object be placed so that a real and inverted image of same size is obtained by a convex lens

(A) f

(B) 2f

(C) Infinity

(D) Between f and 2f

Ans: B

2f

Question: 6

The refractive index of four substances A, B, C and D are 1.31, 1.43, 1.33, 2.4 respectively. The speed of light is maximum in

(A) A

(B) B

(C) C

(D) D

Ans: A

A

Question: 7

The eye defect presbyopia can be corrected by

(A) Bi focal lenses

(B) Convex mirror

(C) Concave lens

(D) Convex lens

Ans: A

Bi focal lenses

Question: 8

In a myopic eye, the image of the object is formed

(A) On the blind spot

(B) On the retina

(C) Behind the retina

(D) In front of the retina

Ans: D

In front of the retina

Question: 9

The least distance of distinct vision is _____

(A) 20 m

(B) 20 cm

(C) 25 cm

(D) 25 m

Ans: C

25 cm

Question: 10

A star appears twinkling in the sky because of ____ by the atmosphere.

(A) Refraction of light

(B) Reflection of light

(C) Scattering of light

(D) Both a and b

Ans: A

Refraction of light