Photoelectric effect was successfully explained first by

The curve drawn between velocity and frequency of photon in vacuum will be a

A convex lens of focal length $40 \mathrm{~cm}$ forms an image of an extended source of light on a photoelectric cell. A current I is produced. The lens is replaced by another convex lens having the same diameter but focal length $20 \mathrm{~cm}$. The photoelectric current now is:

Quantam nature of light is explained by which of the following phenomenon

A $5$ watt source emits monochromatic light of wavelength $5000\; \mathring A$. When placed $0.5\; m$ away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of $1.0\;m$, the number of photo electrons liberated will

When light falls on a metal surface, the maximum kinetic energy of the emitted photo-electrons depends upon