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 spectrum of light emitted by a glowing solid is

An electron is moving through a field. It is moving $(i)$ opposite to an electric field and $(ii)$ perpendicular to a magnetic field as shown. For each situation,determine the de-Broglie wavelength of the electron.

The book “Physics of Physics” was written by

Statement $(I)$ : By increasing the potential difference between cathode and anode continuously in a photoelectric experiment,the photocurrent always increases continuously.
Statement $(II)$ : If two photons $A$ and $B$ of energies $2.5 \ eV$ and $3.5 \ eV$ respectively fall on a metal surface of work function $2.0 \ eV$,then the ratio of maximum kinetic energies emitted between $A$ and $B$ is $3$.
Statement $(III)$ : The maximum energy needed by an electron to come out from metal surface is called the work function of the metal.
Which of the following is correct?

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