Evidence for the wave nature of light cannot be obtained from

Light from a sodium lamp is passed through cold sodium vapours. The spectrum of the transmitted light consists of:

$A$ zone plate of focal length $60\,cm$ behaves as a convex lens. If the wavelength of incident light is $6000\,\mathring{A},$ then the radius of the first half-period zone will be:

$A$ laser beam is used for surgery because it can be...

The difference in the number of wavelengths,when yellow light propagates through air and vacuum columns of the same thickness,is one. Find the thickness of the air column. Given: Refractive index of air $\mu_a = 1.0003$,Wavelength of yellow light in vacuum $\lambda_0 = 6000 \text{ Å}$.

What happens to the intensity of light from a bulb if the distance from the bulb is doubled? As a laser beam travels across the length of a room,its intensity essentially remains constant. What geometrical characteristic of $LASER$ beam is responsible for the constant intensity which is missing in the case of light from the bulb?