Default Title

Question (31)

QN0036302

A convex lens has focal length 10 cm and an object is placed 30 cm in front of it. The image distance is

(A) 10 cm
(B) 15 cm
(C) 20 cm
(D) 30 cm

Correct Answer: B

Explanation:

Using 1/v - 1/u = 1/f with u = -30 cm and f = +10 cm gives v = +15 cm.

Link:

Report Error

Question (32)

QN0036303

A convex lens has focal length 20 cm and an object is placed 60 cm in front of it. The image distance is

(A) 15 cm
(B) 20 cm
(C) 30 cm
(D) 60 cm

Correct Answer: C

Explanation:

Using the lens formula, 1/v = 1/20 - 1/60 = 1/30. Therefore v = +30 cm.

Link:

Report Error

Question (33)

QN0036304

An object is placed 10 cm from a convex lens of focal length 15 cm. The image formed is

(A) real, inverted and diminished
(B) real, inverted and enlarged
(C) virtual, erect and enlarged
(D) virtual, inverted and diminished

Correct Answer: C

Explanation:

The object is inside the focal length, so a convex lens forms a virtual, erect and enlarged image.

Link:

Report Error

Question (34)

QN0036305

An object of height 5 cm is placed at 2F of a convex lens. The image height is

(A) 2.5 cm
(B) 5 cm
(C) 10 cm
(D) 15 cm

Correct Answer: B

Explanation:

An object placed at 2F forms an image of the same size at 2F on the other side of the lens.

Link:

Report Error

Question (35)

QN0036306

A convex lens forms a real image at 40 cm when the object is placed 20 cm in front of it. The focal length of the lens is approximately

(A) 10 cm
(B) 13.3 cm
(C) 20 cm
(D) 30 cm

Correct Answer: B

Explanation:

Using the lens formula, 1/f = 1/40 + 1/20 = 3/40. Hence f = 40/3 ≈ 13.3 cm.

Link:

Report Error

Question (36)

QN0036307

A convex lens of focal length 20 cm has an object placed 30 cm in front of it. If the object height is 3 cm, the image height is

(A) +6 cm
(B) -3 cm
(C) -6 cm
(D) +3 cm

Correct Answer: C

Explanation:

The image distance is 60 cm. Magnification m = v/u = 60/(-30) = -2. Therefore h' = -2 × 3 = -6 cm.

Link:

Report Error

Question (37)

QN0036308

A concave lens has focal length -20 cm and an object is placed 40 cm in front of it. The image distance is approximately

(A) +13.3 cm
(B) +20 cm
(C) -13.3 cm
(D) -40 cm

Correct Answer: C

Explanation:

Using the lens formula with f = -20 cm and u = -40 cm gives v ≈ -13.3 cm.

Link:

Report Error

Question (38)

QN0036309

For the concave lens in the previous question, the magnification is approximately

(A) +0.33
(B) -0.33
(C) +3
(D) -3

Correct Answer: A

Explanation:

m = v/u = (-13.3)/(-40) ≈ +0.33. The positive sign indicates an erect image.

Link:

Report Error

Question (39)

QN0036310

A concave lens always forms an image that is

(A) real, inverted and enlarged
(B) real, erect and diminished
(C) virtual, erect and diminished
(D) virtual, inverted and enlarged

Correct Answer: C

Explanation:

A concave lens forms a virtual, erect and diminished image for a real object.

Link:

Report Error

Question (40)

QN0036311

A lens produces a magnification of -2 for an object of height 4 cm. The image height is

(A) +2 cm
(B) -2 cm
(C) +8 cm
(D) -8 cm

Correct Answer: D

Explanation:

m = h'/h, so h' = m × h = -2 × 4 = -8 cm.

Link:

Report Error

Question (31)

A convex lens has focal length 10 cm and an object is placed 30 cm in front of it. The image distance is

Explanation:

Link:

Question (32)

A convex lens has focal length 20 cm and an object is placed 60 cm in front of it. The image distance is

Explanation:

Link:

Question (33)

An object is placed 10 cm from a convex lens of focal length 15 cm. The image formed is

Explanation:

Link:

Question (34)

An object of height 5 cm is placed at 2F of a convex lens. The image height is

Explanation:

Link:

Question (35)

A convex lens forms a real image at 40 cm when the object is placed 20 cm in front of it. The focal length of the lens is approximately

Explanation:

Link:

Question (36)

A convex lens of focal length 20 cm has an object placed 30 cm in front of it. If the object height is 3 cm, the image height is

Explanation:

Link:

Question (37)

A concave lens has focal length -20 cm and an object is placed 40 cm in front of it. The image distance is approximately

Explanation:

Link:

Question (38)

For the concave lens in the previous question, the magnification is approximately

Explanation:

Link:

Question (39)

A concave lens always forms an image that is

Explanation:

Link:

Question (40)

A lens produces a magnification of -2 for an object of height 4 cm. The image height is

Explanation:

Link:

Excel With Tutors

ExcelWithTutors

For Student

For Tutors

Learn

OUR POLICY