In photoelectric effect if the intensity of light is doubled then maximum kinetic energy of photoelectrons will become

In a photoemissive cell with executing wavelength $\lambda $, the fastest electron has speed $v.$ If the exciting wavelength is changed to $\frac{{3\lambda }}{4}$, the speed of the fastest emitted electron will be

If the energy of a photon is $10\,eV$, then its momentum is

A $160 \,W$ infrared source is radiating light of wavelength $50000 \,\mathring A$ uniformly in all directions. The photon flux at a distance of $1.8 \,m$ is the order of ............. $m^{-2} s ^{-1}$

A silver sphere of radius $1\ cm$ and work function $4.7 \ eV$ is suspended from an insulating thread in free-space. It is under continuous illumination of $200 \ nm$ wavelength light. As photoelectrons are emitted, the sphere gets charged and acquires a potential. The maximum number of photoelectrons emitted from the sphere is $A \times 10^2$ (where $1 < A < 10$ ). The value of  $'Z '$ is

A photon falls through a height of $1 \,km$ through the earth's gravitational field. To calculate the change in its frequency, take its mass to be $h v / c^{2}$. The fractional change in frequency $v$ is close to