Using the Heisenberg uncertainty principle, arrange the following particles in the order of increasing lowest energy possible.

$(I)$ An electron in $H _{2}$ molecule

$(II)$ A hydrogen atom in a $H _{2}$ molecule

$(III)$ A proton in the carbon nucleus

$(IV)$ $A H _{2}$ molecule within a nanotube

Assertion : Photoelectric effect demonstrates the wave nature of light.
Reason : The number of photoelectrons is proportional to the frequency of light.

Photoelectric effect experiments are performed using three different metal plates $\mathrm{p}, \mathrm{q}$ and $\mathrm{r}$ having work functions $\phi_p=2.0 \mathrm{eV}, \phi_q=2.5 \mathrm{eV}$ and $\phi_r=3.0 \mathrm{eV}$, respectively. A light beam containing wavelengths of $550 \mathrm{~nm}, 450 \mathrm{~nm}$ and $350 \mathrm{~nm}$ with equal intensities illuminates each of the plates. The correct I-V graph for the experiment is [Take $h c=1240 \mathrm{eV} \mathrm{nm}$ ]

Photons of energy $6 eV$ are incident on a metal surface whose work function is $4 eV$. The minimum kinetic energy of the emitted photo-electrons will be ........... $eV$

A point source of light is used in an experiment on photoelectric effect. Which of the following curves best represents the variation of photo current $(i)$ with distance $(d)$ of the source from the emitter