Wave Optics

The wavelength of spectral line coming from a distant star shifts from to . The velocity of the star relative to earth is

A glass plate of refractive index is coated with a thin layer of thickness t and refractive index . Light of wavelength travelling in air is incident normally on the layer. It is partly reflected at upper and lower surfaces of the layer and the two reflected rays interfere. The least value of for which the rays interfere constructively is

In Young's double slit experiment using monochromatic light of wavelength . the intensity of light at a point on the screen where path difference is , is units. The intensity of light at a point, where path difference is is