When a convex lens of glass is immersed in water, its power will
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → decrease
Power of a lens is given by:
$P = \left(\frac{n_{lens}}{n_{medium}} - 1\right)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)$
When the lens is in air: $n_{medium} = 1$
When immersed in water: $n_{medium} = 1.33$
Since $\frac{n_{lens}}{n_{medium}} - 1$ decreases in water, the effective power decreases.
Correct option: decrease