The focal length of a convex lens is fL = 10 cm. On immersing in water, it will act as a :

Explanation

When a 10 cm convex lens is immersed in water, its focal length increases by 10 cm, and it still behaves like a convex lens-lens maker’s formula $$ \frac{1}{f} = (\mu - \mu^1) \left[ \frac{1}{R_1} - \frac{1}{R_2} \right] $$ Where the refractive index of the lens ($\mu$) and the refractive index of the medium, ($\mu^1$) and R1 and R2 are the radii of curvature of the lens. f = 10 cm, R1 = R2 = 10 cm, ($\mu$ = 1, $\mu^1$ = 1.33) Since the refractive index of water ($\mu^1$) is greater than the refractive index of air ($\mu$), the value of ($\mu$ – $\mu^1$) decreases and the focal length increases- $$ f \propto \frac{1}{(\mu - \mu^1)} $$