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


1.
The power of a lens is defined as:
A.
The product of focal length and refractive index
B.
The reciprocal of focal length when expressed in centimetres
C.
The reciprocal of focal length when expressed in metres
D.
The square of focal length
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ANSWER :
C. The reciprocal of focal length when expressed in metres
2.
The SI unit of power of a lens is:
A.
Dioptre (1 D = 1 m⁻¹)
B.
Watt
C.
Centimetre
D.
Metre
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ANSWER :
A. Dioptre (1 D = 1 m⁻¹)
3.
A convex lens of focal length 50 cm has power:
A.
-2 D
B.
+2 D
C.
+50 D
D.
+0.5 D
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ANSWER :
B. +2 D
4.
A concave lens of focal length 25 cm has power:
A.
-4 D
B.
-25 D
C.
+4 D
D.
+0.25 D
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ANSWER :
A. -4 D
5.
An optician prescribes a corrective lens of +2.5 D. The required lens is:
A.
Convex lens of focal length 40 cm
B.
Convex lens of focal length 25 cm
C.
Concave lens of focal length 2.5 cm
D.
Concave lens of focal length 40 cm
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ANSWER :
A. Convex lens of focal length 40 cm
6.
A lens of power -4 D has focal length:
A.
+25 cm (convex lens)
B.
-40 cm
C.
-4 cm
D.
-25 cm (concave lens)
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ANSWER :
D. -25 cm (concave lens)