In the photoelectric effect, the stopping potential depends on:

$A$ photon of energy $hv$ is absorbed by a free electron of a metal having work function $\phi < hv$.

On a photosensitive material,when the frequency of incident radiation is increased by $30 \%$,the kinetic energy of emitted photoelectrons increases from $0.4 \ eV$ to $0.9 \ eV$. The work function of the surface is (in $eV$)

The threshold wavelength of a metal is $400 \ nm$. The maximum kinetic energy of the emitted photoelectrons is $1.5 \ eV$. Find the wavelength of the incident photon in $\mathring{A}$.

When a metal plate is illuminated with light of wavelengths $400 \ nm$ and $250 \ nm$,the maximum velocities of the emitted photoelectrons are $v$ and $2v$,respectively. The work function of the metal is ($h$ = Planck's constant; $c$ = speed of light in vacuum):

When the light of frequency $2v_0$ (where $v_0$ is threshold frequency) is incident on a metal plate,the maximum velocity of electrons emitted is $v_1$. When the frequency of the incident radiation is increased to $5v_0$,the maximum velocity of electrons emitted from the same plate is $v_2$. The ratio of $v_1$ to $v_2$ is