Question

why does the focal length of concave lens is changed when dipped in water ?​

Answer 1

Answer:

Explanation:

In case of spherical mirrors (both concave and convex), there will be no change in the focal length of the mirrors when immersed in water. This is because the focal length of mirrors does not depend on the external medium in which it is held.

Answer 2

Answer:

When a lens is immersed in water, the value of refractive index decreases, Hence it's focal length increases

Explanation:

In case of spherical mirrors (both concave and convex), there will be no change in focal length when immersed in the water because the focal length of the mirrors does not depend on the external medium in which it is held. But in case of lenses refraction takes place. when a lense is immersed in the water ,the value of refractive index decreases So it's focal length increases (will change)