According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal versus the frequency, of the incident radiation gives a straight line whose slope

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. Fig. $19.18$

A $200 \mathrm{W}$ sodium street lamp emits yellow light of wavelength $0.6\mathrm{\mu m}$. Assuming it to be $25\%$ efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is:

Two radiations of photons energy $1\mathrm{eV}$ and $2.5\mathrm{eV}$, successively illuminate a photosensitive metallic surface of work function $0.5\mathrm{eV}$. The ratio of the maximum speeds of the emitted electrons is