Question

Explain with reason, how the POWER of a diverging lens changes when (i) it is kept in a medium of refractive index greater than that of the lens. PLS help me on how power changes?

Answer 1

because speed of light is different in different medium. So, bending of light takes place

Answer 2

If diverging lens is kept in a medium with refractive index greater than that, it behaves as converging lens.

Focal length of concave lens is in negative x direction and hence it's power is negative. Now, under greater refractive index medium it changes to positive.

Under that medium value of focal length also changes.

f(med) = f(air).[n₁(n₂-1)] / [n₂-n₁].

Where n₁ is the refractive index of lens and n₂ is the refractive index of medium.

P = 1/f. So take reciprocal of whole equation to get the power of lens in a new medium.