The maximum kinetic energy of emitted electrons in a photoelectric effect does not depend upon

Monochromatic radiation of wavelength $640.2 \;nm$ $(1 \;nm = 10^{-9} \;m)$ from a neon lamp irradiates a photosensitive material made of caesium on tungsten. The stopping voltage is measured to be $0.54 \;V$. The source is replaced by an iron source and its $427.2 \;nm$ line irradiates the same photo-cell. Predict the new stopping voltage (in $V$). (in $;V$)

$A$ beam of electromagnetic radiation of intensity $6.4 \times 10^{-5} \; W/cm^{2}$ is comprised of wavelength $\lambda = 310 \; nm$. It falls normally on a metal surface (work function $\varphi = 2 \; eV$) of surface area $1 \; cm^{2}$. If one in $10^{3}$ photons ejects an electron, the total number of electrons ejected in $1 \; s$ is $10^{x}$. Then $x$ is: $(hc = 1240 \; eV \cdot nm, 1 \; eV = 1.6 \times 10^{-19} \; J)$

$A$ silver ball of radius $4.8 \ cm$ is suspended by a thread in a vacuum chamber. $UV$ light of wavelength $200 \ nm$ is incident on the ball for some time,during which a total energy of $1 \times 10^{-7} \ J$ falls on the surface. Assuming that on average one out of $10^3$ incident photons is able to eject an electron,the potential on the sphere will be ............ $V$.

Photoelectric emission is observed from a metallic surface for frequencies ${\nu _1}$ and ${\nu _2}$ of the incident light rays $({\nu _1} > {\nu _2})$. If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of $1:k$,then the threshold frequency of the metallic surface is

The maximum velocity of the photoelectron emitted by the metal surface is $V$. The charge and mass of the photoelectron are denoted by $e$ and $m$ respectively. The stopping potential in volts is: