Magnification, Power of a Lens, Combination of thin lenses in contact. Refraction of light... NEET Questions

Physics - Optics

Magnification, Power of a Lens, Combination of thin lenses in contact. Refraction of light... MCQ Questions


7.
If the focal length of a lens is doubled, its power becomes:
A.
Double
B.
Half
C.
Four times
D.
One-fourth
šŸ˜‘ View Answer Rough Work Error
ANSWER :
B. Half
8.
A converging lens has power +5 D. Its focal length is:
A.
50 cm
B.
20 cm
C.
0.2 cm
D.
5 cm
šŸ˜‘ View Answer Rough Work Error
ANSWER :
B. 20 cm
9.
When two thin lenses of focal lengths fā‚ and fā‚‚ are placed in contact, the combined focal length f is:
A.
1/f = 1/fā‚ + 1/fā‚‚
B.
f = fā‚ + fā‚‚
C.
f = fā‚ Ɨ fā‚‚
D.
1/f = 1/fā‚ - 1/fā‚‚
šŸ˜‘ View Answer Rough Work Error
ANSWER :
A. 1/f = 1/fā‚ + 1/fā‚‚
10.
When several thin lenses are in contact, the total power of the combination is:
A.
P = Pā‚ Ɨ Pā‚‚ Ɨ Pā‚ƒ Ɨ ...
B.
P = āˆš(Pā‚Ā² + Pā‚‚Ā² + Pā‚ƒĀ² + ...)
C.
P = Pā‚ + Pā‚‚ + Pā‚ƒ + ... (algebraic sum)
D.
P = max(Pā‚, Pā‚‚, Pā‚ƒ, ...)
šŸ˜‘ View Answer Rough Work Error
ANSWER :
C. P = Pā‚ + Pā‚‚ + Pā‚ƒ + ... (algebraic sum)
11.
Two convex lenses of focal lengths 20 cm and 30 cm are placed in contact. The equivalent focal length is:
A.
12 cm
B.
10 cm
C.
50 cm
D.
60 cm
šŸ˜‘ View Answer Rough Work Error
ANSWER :
A. 12 cm
12.
A convex lens of focal length 20 cm is in contact with a concave lens of focal length 30 cm. The combination has focal length:
A.
10 cm (converging)
B.
60 cm (diverging)
C.
60 cm (converging)
D.
12 cm (converging)
šŸ˜‘ View Answer Rough Work Error
ANSWER :
C. 60 cm (converging)