$A$ photon incident on a metal of work function $2 \text{ eV}$ produces photoelectrons of maximum kinetic energy of $2 \text{ eV}$. The wavelength associated with the photon is: (in $\text{ Å}$)

The following graph shows the variation of stopping potential with the frequency of incident radiation $(v)$ for a given metal. The correct variation is shown in graph [$v_0 =$ threshold frequency].

The beam of light has three wavelengths $4144 \,\mathring A$,$4972 \,\mathring A$,and $6216 \,\mathring A$ with a total intensity of $3.6 \times 10^{-5} \, W/m^2$ equally distributed amongst the three wavelengths. The beam falls normally on an area of $1 \, cm^2$ of a clean metallic surface with a work function of $2.3 \, eV$. Assume that there is no loss of light by reflection and that each energetically capable photon ejects one electron. Calculate the number of photoelectrons liberated in $2 \, s$.

Light of frequency $4v_0$ is incident on a metal surface with a threshold frequency $v_0$. The maximum kinetic energy of the emitted photoelectrons is:

For two different photosensitive materials having work functions $\phi$ and $2 \phi$ respectively,which are illuminated with light of sufficient energy to emit electrons,if the graph of stopping potential $(V_s)$ versus frequency $(\nu)$ is drawn for these two materials,what is the ratio of the slopes of the graphs for these two materials?

The photoelectric threshold wavelength for potassium (work function being $2 \ eV$) is ........... $nm$.