Find the maximum magnitude of the linear momentum of a photoelectron emitted when light of wavelength $400 \, nm$ falls on a metal having a work function of $2.5 \, eV$.

$A$ 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 ......... $eV$. $(hc = 1240 \ eV \cdot nm)$

For zero photoelectric current,the stopping potential is:

In a photoelectric emission experiment,the stopping potential for a given metal is $V$ volt,when radiation of wavelength $\lambda$ is used. If radiation of wavelength $2 \lambda$ is used with the same metal,then the stopping potential (in volt) will be. [Given: $c = \text{velocity of light}$,$e = \text{charge on electron}$,$h = \text{Planck's constant}$]

In a photoelectric experiment,the wavelength of the light incident on a metal is changed from $300\, nm$ to $400\, nm$. The decrease in the stopping potential is close to ................ $V$ $\left( \frac{hc}{e} = 1240\, nm \cdot V \right)$

Let $K_{1}$ and $K_{2}$ be the maximum kinetic energies of photo-electrons emitted when two monochromatic beams of wavelength $\lambda_{1}$ and $\lambda_{2}$,respectively,are incident on a metallic surface. If $\lambda_{1} = 3 \lambda_{2}$,then: