The minimum wavelength of $$X$$-rays produced by an electron accelerated through a potential difference of $$V$$ volts is proportional to :

The light rays having photons of energy 4.2 eV are falling on a metal surface having a work function of 2.2 eV. The stopping potential of the surface is

The threshold frequency of a photoelectric metal is v₀. If light of frequency 4v₀ is incident on this metal, then the maximum kinetic energy of emitted electrons will be :

When two monochromatic lights of frequency, v and $${v \over 2}$$ are incident on a photoelectric metal, their stopping potential becomes $${{{V_s}} \over 2}$$ and V_s respectively. The threshold frequency for this metal is