Question

What will happen to newton's rings if lens is lifted up slowly?

Answer 1

ANSWER

As the lens is lifted the difference in optical path between the two reflected rays will vary, thus slowly converting bright rings to dark and vice versa. This will be periodic change. If the wavelength of the incident light is V, and d is the distance by which the lens is lifted, then:

Bright and dark rings will be interchanged when d=(2n+1) V and the rings will revert to original position when d=2nV for any integer V. These two cases correspond to phase differences of pi and 2pi.

HOPE IT HELPS ✔️