The photoelectric work function for a metal surface is $4.125 \ eV$. The cut-off wavelength for this surface is .......... $\mathring{A}$.

An electron in a Hydrogen atom jumps from the second Bohr orbit to the ground state, and the difference between the energies of the two states is radiated in the form of a photon. This photon strikes a material. If the work function of the material is $4.2 \ eV$, then the stopping potential is (Energy of electron in $n$-th orbit $= -\frac{13.6}{n^2} \ eV$). (in $V$)

What is the threshold frequency of a metal with a work function of $1.65 \ eV$?

The energy of the incident photon on a metal surface is $3W$ and then $5W$,where $W$ is the work function of that metal. The ratio of the maximum velocities of the emitted photoelectrons is:

An isolated lead ball is charged upon continuous irradiation by $EM$ radiation of wavelength, $\lambda = 221 \,nm$. The maximum potential attained by the lead ball, if its work function is $4.14 \,eV$, is (take, $h = 6.63 \times 10^{-34} \,J \cdot s$, $c = 3 \times 10^8 \,m/s$, $e = 1.6 \times 10^{-19} \,C$): (in $\,V$)

$A$ photosensitive metallic surface is illuminated alternately with lights of wavelength $3100 \mathring A$ and $6200 \mathring A$. It is observed that the maximum speeds of the photoelectrons in the two cases are in the ratio $2:1$. The work function of the metal is $(hc = 12400 \, eV \mathring A)$.