Two thin symmetrical lenses of different nature and of different material have equal radii of curvature R=15cm. The lenses are put close together and immersed in water (μw=4/3). The focal length of the system in water is 30cm. The difference between refractive indices of the two lenses is
1/2
1/4
1/3
3/4
A
1/2
B
1/4
C
1/3
D
3/4
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Solution
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focal length be f=30
4/3−μ1R+μ2−4/3R=1f
Δμ15=130
Δμ=12
option A is correct
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