Which of the following phenomena support the wave theory of light?
$(1)$ Scattering
$(2)$ Interference
$(3)$ Diffraction
$(4)$ Velocity of light in a denser medium is less than the velocity of light in a rarer medium

$\lambda_{1}$ and $\lambda_{2}$ are used to illuminate the slits. $\beta_{1}$ and $\beta_{2}$ are the corresponding fringe widths. The wavelength $\lambda_{1}$ can produce photoelectric effect when incident on a metal. But the wavelength $\lambda_{2}$ cannot produce photoelectric effect. The correct relation between $\beta_{1}$ and $\beta_{2}$ is

$A$ 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:

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?

$A$ laser beam is used for carrying out surgery because it

According to the corpuscular theory of light,which of the following phenomena can be explained?