If a photocell is illuminated with a radiation of 1240 $$\mathop A\limits^o $$, the stopping potential is found to be 8V. Then, the work-function of the emitter and the threshold wavelength are

The graph between the maximum speed $$(v_{max})$$ of a photoelectron and frequency $$(\nu)$$ of the incident radiation, in photoelectric effect is correctly represented by

The de-Broglie wavelength associated with a proton under the influence of an electric potential of 100 V is

Radiation of wavelength $$300 \mathrm{~nm}$$ and intensity $$100 \mathrm{~W}-\mathrm{m}^{-2}$$ falls on the surface of a photosensitive material. If $$2 \%$$ of the incident photons produce photoelectron, the number of photoelectrons emitted from an area of $$2 \mathrm{~cm}^2$$ of the surface is nearly