Question

a concave lens having focal length 10 cm is placed in water what it the focal length in water​

Answer 1

Answer:

whenver a lens is kept in a denser

medium its focal lenght

increases

Answer 2

The focal length will increase.

The refractive index of the material of lens with respect to water(u=1.33) will be lesser than with air(u=1) and hence the deviation would be less inside water as compared to air. This results in light converging at much more distance than earlier and hence increasing focal length.

Therefore the focal length of the concave lens would increase in water as compared to the lens surrounded by air.