When a thin convergent glass lens ( μ g = 1.5 ) and has power of +5 D is immersed in a liquid of refractive index μ ℓ it acts as a divergent lens of focal length 100 cm. Then μ ℓ is :

Question

When a thin convergent glass lens ( μ g ​ = 1.5 ) and has power of +5 D is immersed in a liquid of refractive index μ ℓ ​ it acts as a divergent lens of focal length 100 cm. Then μ ℓ ​ is :

TestHub · Accepted Answer

In air: P = ( μ g ​ − 1 ) K = 5 D. In liquid: f = − 100 cm , so P ′ = ( μ ℓ ​ μ g ​ ​ − 1 ) K = − 1 D. ( μ g ​ − 1 ) ( μ g ​ / μ ℓ ​ − 1 ) ​ = − 5 1 ​ ⇒ μ ℓ ​ 1.5 ​ − 1 = − 0.1 μ ℓ ​ = 0.9 1.5 ​ = 3 5 ​ . Option (B).

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