Question

A convex lens of glass $(\mu = 15)$ has a local length of 8 cm when placed in air. What is the strength of lens when it is immersed in water $\bigg(\mu = \frac{4}{3}\bigg) ?$

• A. 4 cm
• B. 8 cm
• C. 16 cm
• D. 32 cm

Answer 1

Answer: (D)

32 cm

Answer 2

$f_{water} = 4 \times f_{air} = 4 \times 8 = 32\, cm$