Question

A thin convergent glass lens (= 1.5) has a power of +5.0 D. When this lens is immersed in a liquid of refractive index μ, it acts as a divergent lens of focal length 100 cm. The value of μ must be:

• A. (4)/(3)
• B. (5)/(3)
• C. (5)/(4)
• D. (6)/(5)

Hint:

A converging lens can behave as diverging if surrounding medium has higher refractive index.

Answer 1

The Correct Option is B

Step 1: Power of lens in air. P = ( - 1)((1)/(R₁) - (1)/(R₂)) = 5
Step 2: Power of lens in liquid. P' = (()/(μ) - 1)((1)/(R₁) - (1)/(R₂))
Step 3: Given focal length in liquid. P' = -1 D
Step 4: Solving ratio. (P')/(P) = ()/(μ) - 1 - 1 μ = (5)/(3)