When green light is incident on the surface of a metal, it emits photo-electrons, but there is no such emission with yellow light. Which one of the following colors can produce the emission of photo-electrons?

$4 \ eV$ is the energy of the incident photon and the work function is $2 \ eV$. What is the stopping potential in $V$?

Two light waves of wavelengths $600 \,nm$ and $200 \,nm$ are incident on a metal surface. The maximum velocity of photoelectrons produced due to one wavelength is $\frac{1}{3}$ of the maximum velocity of the photoelectrons produced due to the other wavelength. The work function of the metal is:

When light of frequency twice the threshold frequency is incident on a metal plate,the maximum velocity of the emitted electron is $v_{1}$. When the frequency of incident radiation is increased to five times the threshold value,the maximum velocity of the emitted electron becomes $v_{2}$. If $v_{2} = x v_{1}$,the value of $x$ will be...........

When radiation of wavelength $400 \ nm$ is incident on a metal surface,the kinetic energy of the emitted photoelectrons is $1.68 \ eV$. The work function of the metal is .......... $eV$.

$A$ metal surface is illuminated by radiation of wavelength $4500 \; \mathring A$. The ejected photoelectron enters a constant magnetic field of $2 \; mT$ making an angle of $90^{\circ}$ with the magnetic field. If it starts revolving in a circular path of radius $2 \; mm$,the work function of the metal is approximately ............. $eV$.