A caesium photocell, with a steady potential difference of $60V$ across, is illuminated by a bright point source of light $50 cm$ away. When the same light is placed 1m away the photoelectrons emitted from the cell
Are one quarter as numerous
Are half as numerous
Each carry one quarter of their previous momentum
Each carry one quarter of their previous energy
A Laser light of wavelength $660\,nm$ is used to weld Retina detachment. If a Laser pulse of width $60\, ms$ and power $0.5\, kW$ is used the approximate number of photons in the pulse are : [Take Planck's constant $h\, = 6.62\times10^{- 34}\, Js$]
Ultraviolet light of wavelength $300 \ nm$ and intensity $1.0 \ watt/m^2$ falls on the surface of a photosensitive material. If $1\%$ of the incident photons produce photoelectrons, then the number of photoelectrons emitted from an area of $1.0\ cm^2$ of the surface is nearly
Kinetic energy with which the electrons are emitted from the metal surface due to photoelectric effect is
If the total energy transferred to a surface in time $t$ is $6.48 \times 10^5 \mathrm{~J}$, then the magnitude of the total momentum delivered to this surface for complete absorption will be :