When a point source of light is at a distance of $1 \ m$ from a photocell,the cut-off voltage is found to be $V$. If the same source is placed at $2 \ m$ distance from the photocell,the cut-off voltage will be

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 $V$)

Photoemission from a metal surface takes place for frequencies $v_1$ and $v_2$ of incident rays. If the ratio of the maximum kinetic energy of photoelectrons is $1:K$,then the threshold frequency of the metallic surface is

When the wavelength of radiation falling on a metal is changed from $500 \, nm$ to $200 \, nm$,the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to $..... \, eV$.

Light of wavelength $\lambda$ is incident on the surface of a metal having work function $\phi$, causing the emission of electrons. What is the maximum velocity of the emitted electrons? (Given: $c = \text{velocity of light}$, $h = \text{Planck's constant}$, $m = \text{mass of electron}$)

The work function of a metal is $1 \; eV$. Light of wavelength $3000 \; \mathring{A}$ is incident on this metal surface. The velocity of the emitted photo-electrons will be: