Lenses
Q. A biconvex lens has a radius of curvature of 10 cm on both sides. What is its focal length?
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
Show solution
Solution
Using the lens maker's formula, f = R/2(n-1). Here, R = 10 cm, n = 1.5, so f = 10/(2(1.5-1)) = 10/1 = 10 cm.
Correct Answer: B — 10 cm
Learn More →
Q. A biconvex lens has a radius of curvature of 30 cm on both sides. What is the focal length of the lens if the refractive index is 1.5?
A.
10 cm
B.
15 cm
C.
20 cm
D.
25 cm
Show solution
Solution
Using the lens maker's formula, f = R/(n-1) = 30/(1.5-1) = 30/0.5 = 60 cm.
Correct Answer: B — 15 cm
Learn More →
Q. A biconvex lens has radii of curvature 20 cm and 30 cm. What is the focal length of the lens?
A.
10 cm
B.
15 cm
C.
25 cm
D.
50 cm
Show solution
Solution
Using the lens maker's formula, the focal length is calculated to be 15 cm.
Correct Answer: B — 15 cm
Learn More →
Q. A concave lens has a focal length of -12 cm. What is the image distance when the object is placed at 24 cm?
A.
8 cm
B.
12 cm
C.
16 cm
D.
20 cm
Show solution
Solution
Using the lens formula, 1/f = 1/v - 1/u, we find v = 8 cm.
Correct Answer: A — 8 cm
Learn More →
Q. A concave lens has a focal length of 25 cm. What is the image distance when the object is placed at 50 cm?
A.
-16.67 cm
B.
-25 cm
C.
-50 cm
D.
-75 cm
Show solution
Solution
Using the lens formula, the image distance is calculated to be -16.67 cm.
Correct Answer: A — -16.67 cm
Learn More →
Q. A convex lens has a focal length of 20 cm. What is the power of the lens?
A.
-5 D
B.
5 D
C.
20 D
D.
0.05 D
Show solution
Solution
Power (P) = 1/f (in meters). f = 20 cm = 0.2 m, so P = 1/0.2 = 5 D.
Correct Answer: B — 5 D
Learn More →
Q. A diverging lens has a focal length of -10 cm. What is the image distance when the object is placed at 5 cm?
A.
-3.33 cm
B.
-5 cm
C.
3.33 cm
D.
5 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, we have 1/(-10) = 1/v - 1/5. Solving gives v = -3.33 cm.
Correct Answer: A — -3.33 cm
Learn More →
Q. A double convex lens has a radius of curvature of 20 cm on both sides. What is its focal length if the refractive index is 1.5?
A.
10 cm
B.
15 cm
C.
20 cm
D.
25 cm
Show solution
Solution
Using the lens maker's formula, f = R/(n-1), we find f = 20/(1.5-1) = 40 cm.
Correct Answer: A — 10 cm
Learn More →
Q. A lens forms a real image of a height 5 cm at a distance of 40 cm from the lens. If the object is placed at 20 cm from the lens, what is the height of the object?
A.
2.5 cm
B.
5 cm
C.
10 cm
D.
20 cm
Show solution
Solution
Using the magnification formula, m = h'/h = -v/u. Here, h' = 5 cm, v = 40 cm, u = -20 cm. Thus, h = (h' * u) / v = (5 * -20) / 40 = 2.5 cm.
Correct Answer: C — 10 cm
Learn More →
Q. A lens forms a real image of an object placed at a distance of 60 cm from it. If the image distance is 15 cm, what is the focal length of the lens?
A.
10 cm
B.
12 cm
C.
20 cm
D.
25 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, we have 1/f = 1/15 - 1/60. Solving gives f = 10 cm.
Correct Answer: A — 10 cm
Learn More →
Q. A lens forms a real image that is twice the size of the object. If the object is placed 10 cm from the lens, what is the focal length of the lens?
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
Show solution
Solution
Using the lens formula and magnification, we find the focal length to be 15 cm.
Correct Answer: C — 15 cm
Learn More →
Q. A lens forms a virtual image at a distance of 10 cm when the object is placed at 5 cm. What type of lens is it?
A.
Convex lens
B.
Concave lens
C.
Bifocal lens
D.
Plano-convex lens
Show solution
Solution
A virtual image is formed by a concave lens when the object is placed within its focal length.
Correct Answer: B — Concave lens
Learn More →
Q. A lens forms a virtual image at a distance of 12 cm when the object is placed at 8 cm. What is the focal length of the lens?
A.
4 cm
B.
6 cm
C.
8 cm
D.
10 cm
Show solution
Solution
Using the lens formula, 1/f = 1/v - 1/u, we find f = 4 cm.
Correct Answer: A — 4 cm
Learn More →
Q. A lens forms a virtual image at a distance of 20 cm from the lens when the object is placed at 10 cm. What is the focal length of the lens?
A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, where v = -20 cm and u = -10 cm, we find f = 5 cm.
Correct Answer: A — 5 cm
Learn More →
Q. A lens forms a virtual image at a distance of 20 cm when the object is placed at 10 cm. What is the type of lens?
A.
Convex lens
B.
Concave lens
C.
Bifocal lens
D.
Plano-convex lens
Show solution
Solution
A virtual image formed by a lens indicates that it is a concave lens.
Correct Answer: B — Concave lens
Learn More →
Q. A lens has a focal length of -10 cm. What type of lens is it?
A.
Convex lens
B.
Concave lens
C.
Biconvex lens
D.
Biconcave lens
Show solution
Solution
A negative focal length indicates that the lens is a concave lens.
Correct Answer: B — Concave lens
Learn More →
Q. A lens has a focal length of 50 cm. If an object is placed at 100 cm, what type of image is formed?
A.
Real and inverted
B.
Virtual and erect
C.
Real and erect
D.
Virtual and inverted
Show solution
Solution
Since the object distance is greater than the focal length, a real and inverted image is formed.
Correct Answer: A — Real and inverted
Learn More →
Q. A lens has a power of +2.0 D. What is its focal length?
A.
50 cm
B.
25 cm
C.
20 cm
D.
10 cm
Show solution
Solution
Power (P) = 1/f (in meters), so f = 1/2.0 = 0.5 m = 50 cm.
Correct Answer: B — 25 cm
Learn More →
Q. A lens has a power of +2.5 D. What is its focal length?
A.
40 cm
B.
25 cm
C.
50 cm
D.
20 cm
Show solution
Solution
Power (P) = 1/f (in meters). Therefore, f = 1/2.5 = 0.4 m = 40 cm.
Correct Answer: B — 25 cm
Learn More →
Q. A lens has a power of +2.5 D. What is the focal length of the lens in meters?
A.
0.4 m
B.
0.5 m
C.
0.6 m
D.
0.7 m
Show solution
Solution
Power (P) = 1/f, so f = 1/P = 1/2.5 = 0.4 m.
Correct Answer: B — 0.5 m
Learn More →
Q. A lens has a power of +5 diopters. What is its focal length?
A.
20 cm
B.
25 cm
C.
30 cm
D.
15 cm
Show solution
Solution
Power (P) = 1/f (in meters). Therefore, f = 1/P = 1/5 = 0.2 m = 20 cm.
Correct Answer: A — 20 cm
Learn More →
Q. A lens has a power of -4 D. What is the type of lens?
A.
Convex
B.
Concave
C.
Bifocal
D.
Plano-convex
Show solution
Solution
A negative power indicates a concave lens.
Correct Answer: B — Concave
Learn More →
Q. A lens has a power of -4 D. What type of lens is it?
A.
Convex lens
B.
Concave lens
C.
Bifocal lens
D.
Plano-convex lens
Show solution
Solution
A negative power indicates that the lens is a concave lens.
Correct Answer: B — Concave lens
Learn More →
Q. A lens produces a magnification of 3. If the object height is 2 cm, what is the image height?
A.
4 cm
B.
6 cm
C.
3 cm
D.
2 cm
Show solution
Solution
Magnification (m) = h'/h, thus h' = m * h = 3 * 2 = 6 cm.
Correct Answer: A — 4 cm
Learn More →
Q. A lens produces a virtual image at a distance of 12 cm when the object is placed at 8 cm. What type of lens is it?
A.
Convex
B.
Concave
C.
Biconvex
D.
Biconcave
Show solution
Solution
A virtual image is formed by a concave lens when the object is placed in front of it.
Correct Answer: B — Concave
Learn More →
Q. An object is placed 25 cm from a convex lens of focal length 10 cm. Where is the image formed?
A.
10 cm
B.
15 cm
C.
20 cm
D.
30 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, we find v = 20 cm.
Correct Answer: C — 20 cm
Learn More →
Q. An object is placed 30 cm from a concave lens of focal length 15 cm. What is the nature of the image formed?
A.
Real and inverted
B.
Virtual and erect
C.
Real and erect
D.
Virtual and inverted
Show solution
Solution
For a concave lens, the image formed is virtual and erect when the object is placed in front of it.
Correct Answer: B — Virtual and erect
Learn More →
Q. An object is placed 40 cm from a convex lens with a focal length of 10 cm. Where is the image formed?
A.
At 10 cm
B.
At 20 cm
C.
At 30 cm
D.
At 40 cm
Show solution
Solution
Using the lens formula, the image is formed at 30 cm on the opposite side.
Correct Answer: C — At 30 cm
Learn More →
Q. An object is placed 50 cm from a converging lens of focal length 25 cm. Where will the image be formed?
A.
16.67 cm
B.
33.33 cm
C.
25 cm
D.
20 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, we find v = 33.33 cm.
Correct Answer: B — 33.33 cm
Learn More →
Q. An object is placed at a distance of 40 cm from a convex lens of focal length 20 cm. Where will the image be formed?
A.
10 cm
B.
20 cm
C.
30 cm
D.
40 cm
Show solution
Solution
Using the lens formula 1/f = 1/v - 1/u, we find v = 10 cm.
Correct Answer: A — 10 cm
Learn More →
Showing 1 to 30 of 73 (3 Pages)
