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Question (21)

QN0036292

The refractive index of a medium is 1.5. The speed of light in that medium is

(A) 4.5 × 10^8 m/s
(B) 3 × 10^8 m/s
(C) 2 × 10^8 m/s
(D) 1.5 × 10^8 m/s

Correct Answer: C

Explanation:

v = c/n = (3 × 10^8)/1.5 = 2 × 10^8 m/s.

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Question (22)

QN0036293

When a ray of light is incident normally on a glass surface, it

(A) bends towards the normal
(B) bends away from the normal
(C) passes without deviation
(D) gets completely reflected

Correct Answer: C

Explanation:

At normal incidence, the angle of incidence is zero, so the ray passes through without deviation.

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Question (23)

QN0036294

When light passes through a rectangular glass slab, the emergent ray is generally

(A) perpendicular to the incident ray
(B) parallel to the incident ray but laterally displaced
(C) completely reflected
(D) parallel to the normal

Correct Answer: B

Explanation:

The emergent ray from a rectangular glass slab is parallel to the incident ray but is shifted sideways, producing lateral displacement.

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Question (24)

QN0036295

A coin placed at the bottom of a water-filled vessel appears raised when viewed from above because of

(A) reflection
(B) dispersion
(C) refraction
(D) diffraction

Correct Answer: C

Explanation:

Refraction at the water-air interface makes the apparent depth of the coin less than its actual depth.

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Question (25)

QN0036296

Which of the following represents a pair in which the first medium is optically denser than the second?

(A) Water and diamond
(B) Diamond and water
(C) Air and glass
(D) Water and air

Correct Answer: B

Explanation:

Diamond has a higher refractive index than water, so diamond is optically denser than water.

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Question (26)

QN0036297

A ray travels from glass to air. As the angle of incidence is increased, the refracted ray bends

(A) towards the normal
(B) farther away from the normal
(C) towards the surface of the glass only
(D) without changing direction

Correct Answer: B

Explanation:

Light travelling from a denser to a rarer medium bends away from the normal, with the angle of refraction increasing as incidence increases.

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Question (27)

QN0036298

A medium has refractive index 1.25. The speed of light in this medium is what fraction of its speed in vacuum?

(A) 1/2
(B) 2/3
(C) 4/5
(D) 5/4

Correct Answer: C

Explanation:

Since n = c/v, v/c = 1/n = 1/1.25 = 4/5.

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Question (28)

QN0036299

A ray of light enters glass from air with an angle of incidence of 30° and angle of refraction of 19°. The refractive index of glass is approximately

(A) 1.20
(B) 1.33
(C) 1.53
(D) 2.00

Correct Answer: C

Explanation:

By Snell's law, n = sin 30°/sin 19° ≈ 0.5/0.326 ≈ 1.53.

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Question (29)

QN0036300

A convex lens has a focal length of 25 cm. Its power is

(A) +2 D
(B) +4 D
(C) -4 D
(D) -2 D

Correct Answer: B

Explanation:

f = 25 cm = 0.25 m. Therefore P = 1/f = 1/0.25 = +4 D.

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Question (30)

QN0036301

A lens has a power of -5 D. Its focal length is

(A) +20 cm
(B) -20 cm
(C) +5 cm
(D) -5 cm

Correct Answer: B

Explanation:

f = 1/P = 1/(-5) m = -0.2 m = -20 cm.

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Question (21)

The refractive index of a medium is 1.5. The speed of light in that medium is

Explanation:

Link:

Question (22)

When a ray of light is incident normally on a glass surface, it

Explanation:

Link:

Question (23)

When light passes through a rectangular glass slab, the emergent ray is generally

Explanation:

Link:

Question (24)

A coin placed at the bottom of a water-filled vessel appears raised when viewed from above because of

Explanation:

Link:

Question (25)

Which of the following represents a pair in which the first medium is optically denser than the second?

Explanation:

Link:

Question (26)

A ray travels from glass to air. As the angle of incidence is increased, the refracted ray bends

Explanation:

Link:

Question (27)

A medium has refractive index 1.25. The speed of light in this medium is what fraction of its speed in vacuum?

Explanation:

Link:

Question (28)

A ray of light enters glass from air with an angle of incidence of 30° and angle of refraction of 19°. The refractive index of glass is approximately

Explanation:

Link:

Question (29)

A convex lens has a focal length of 25 cm. Its power is

Explanation:

Link:

Question (30)

A lens has a power of -5 D. Its focal length is

Explanation:

Link:

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