$A$ metal surface is illuminated by light of wavelength $400 \ nm$. The kinetic energy of the emitted photoelectrons is found to be $1.68 \ eV$. The work function of the metal is ......... $eV$. $(hc = 1240 \ eV \cdot nm)$

In a photoelectric effect experiment,the graph of stopping potential $V$ versus the reciprocal of wavelength $(1/\lambda)$ is shown in the figure. As the intensity of incident radiation is increased:

In the photoelectric effect,if the intensity of light is doubled,then the maximum kinetic energy of the photoelectrons will become:

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 $\mathring{A}$.

The electron in the hydrogen atom jumps from excited state $(n = 3)$ to its ground state $(n = 1)$ and the photons thus emitted irradiate a photosensitive material. If the work function of the material is $5.1 \, eV$,the stopping potential is estimated to be (the energy of the electron in $n^{th}$ state $E_n = \frac{-13.6}{n^2} \, eV$) (in $, V$)

$A$ photocell is illuminated by a $100 \ W$ mercury source. It emits ultraviolet light of wavelength $2271 \ \mathring A$. If the stopping potential is $1.3 \ V$,find the work function of the metal in $eV$.