A conversing lens has a focal length of 20cm in air. It is made of a material of refractive index 1.6. If it is immersed in a liquid of refractive index 1.3, find the new focal length.
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Updated on : 2022-09-05
Solution
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Correct option is A)
Converging lens of focal length = +20cm in air μL=1.6
F1=(μMμL−1)(R11−R21) = Lens formula
Where μL→ refractive index of lens
μM→ refractive index of medium
In air (μM=1)
201=(11.6−1)(R11−R21)
201=0.6(R11−R21)
121=(R11−R21)
In liquid (μM=1.3)
F1=(1.31.6−1)(R11−R21)
F1=1.30.3×121
F1=521
Hence,
new focal length is 52 cm
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