Thin Lens Formula and Lens Maker Formula NEET Questions

Physics - Optics

Thin Lens Formula and Lens Maker Formula MCQ Questions


13.
A double convex lens of refractive index 1.5 has R₁ = 10 cm and R₂ = -15 cm. Its focal length is:
A.
30 cm
B.
6 cm
C.
12 cm
D.
25 cm
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ANSWER :
C. 12 cm
14.
An equiconvex lens has focal length 20 cm and refractive index 1.5. The radius of curvature of each face is:
A.
40 cm
B.
10 cm
C.
20 cm
D.
30 cm
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ANSWER :
C. 20 cm
15.
A double convex lens has R₁ = R₂ = 20 cm and focal length 20 cm in air. The refractive index of the lens material is:
A.
1.25
B.
2.0
C.
1.33
D.
1.5
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ANSWER :
D. 1.5
16.
A convex lens has focal length 12 cm with R₁ = +10 cm, R₂ = -15 cm. The refractive index of the material is:
A.
1.33
B.
1.5
C.
1.25
D.
1.6
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ANSWER :
B. 1.5
17.
A glass lens (n = 1.5) has a focal length of 20 cm in air. When placed in water (n = 4/3), the new focal length is approximately:
A.
10 cm
B.
20 cm
C.
80 cm
D.
60 cm
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ANSWER :
C. 80 cm
18.
A convex lens of refractive index 1.5 is immersed in a liquid of refractive index 1.5. The lens behaves as:
A.
A convex lens with same focal length
B.
A concave lens
C.
A convex lens with halved focal length
D.
A plane glass plate (no focusing power, focal length infinite)
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ANSWER :
D. A plane glass plate (no focusing power, focal length infinite)