Question

State whether true or false:

The focal length of a given lens depends on the surrounding medium.

• A. True
• B. False

Answer 1

The correct option is A True

The curvature of surface and the difference in refractive index (of the material of lens and of the surrounding media), are what determine the focal length of a lens. Water has a higher refractive index than air, but lower than glass, so a glass lens placed in water will act similar to what a thinner lens would in air.