Photon of frequency $$v$$ has a momentum associated with it. If $$c$$ is the velocity of light, the momentum is

The threshold frequency for a metallic surface corresponds to an energy of $$6.2$$ $$eV$$ and the stopping potential for a radiation incident on this surface is $$5V.$$ The incident radiation lies in

The anode voltage of a photocell is kept fixed. The wavelength $$\lambda $$ of the light falling on the cathode is gradually changed. The plate current $${\rm I}$$ of the photocell varies as follows

The time taken by a photoelectron to come out after the photon strikes is approximately