The work function of a metal 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 $\,V$)

The stopping potential for photoelectrons:

The threshold wavelength for photoelectric emission from a material is $5200 \, \mathring{A}$. Photo-electrons will be emitted when this material is illuminated with monochromatic radiation from a

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

Einstein received the Nobel Prize for which of the following works?