The dual nature of light is exhibited by

When a monochromatic point source of light is placed at $0.1\, m$ from a photocell,the cut-off voltage and saturation current are $0.8\, V$ and $24\, mA$ respectively. If the same source is placed at $0.2\, m$ away from the photocell,then the cut-off voltage and saturation current will be:

The radiation corresponding to $3 \rightarrow 2$ transition of a hydrogen atom falls on a metal surface to produce photoelectrons. These electrons are made to enter a magnetic field of $3 \times 10^{-4} \ T$. If the radius of the largest circular path followed by these electrons is $10.0 \ mm$,the work function of the metal is close to......$ eV$.

In an experiment on the photoelectric effect,plates of three different metals $p, q,$ and $r$ are used,with work functions $\phi_p = 2.0\ eV$,$\phi_q = 2.5\ eV$,and $\phi_r = 3.0\ eV$,respectively. Three radiations of equal intensity with wavelengths $550\ nm, 450\ nm,$ and $350\ nm$ are incident on these plates. Which of the following $I \rightarrow V$ graphs is correct for the experimental results? $(hc = 1240\ eV\ nm)$

Some laws/processes are given in Column $I$. Match these with the physical phenomena given in Column $II$.

Column $I$	Column $II$
$(A)$ Transition between two atomic energy levels	$(p)$ Characteristic $X$-rays
$(B)$ Electron emission from a material	$(q)$ Photoelectric effect
$(C)$ Mosley's law	$(r)$ Hydrogen spectrum
$(D)$ Change of photon energy into kinetic energy of electrons	$(s)$ $\beta$-decay

The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current $I$ of the photocell varies as follows: