Question

1.a concave mirror and convex lens are held in water.what change,if any,do you expect to find in the focal lenght of either?give reasons.

2.for a real image in a convex lens of focal lenght f,what is the minimum distance between the object and the image?

Answer 1

1) no change in focal length becoz focal length is just the half of the radius of curvature of the imaginary sphere which is not affected by this..
2) I am not sure in this