Explain two ways of emission of electrons from metal surfaces.

Red light, however bright, it cannot produce the emission of electrons from a clean zinc surface, but even weak from a clean zinc surfaces, but even weak ultraviolet radiation can do so, why?

Work function of a metl surface is 4.2 eV. The maximum wavelength which can eject electrons from this metal surface is:

Blue light can eject electrons from a photo sensitive surface while orange light can not. Will violet and red light eject electrons from the metal surface?

Find the frequency of light which ejects electrons from a metal surface, fully stopped by a retarding potential of 3 V. The photoelectric effect brings in this metal at a frequency of 6 xx 10^14 Hz . Find the work function for this metal (Given h=6.63 xx 10^-34 Js) /

Electrons ar emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 A^(@). Calculate threshold frequency (v _(0)) and work function (w) of the metal.

Explain catalytic properties in the transition metals.