Write Einstein's photoelectric equation and point out any two characteristic properties of photons on which this equation is based.

Explanation

(a) Einstein's photoelectric effect equation :
`h v = phi_(0) + K.E`
where,
h `rarr` Planck's constant,
v `rarr` frequency of the incoming photons.
`phi_(0) rarr` work function of the material and
K.E `rarr` Kinetic energy
(b) The two characteristic properties of photons on which this equation is based are as follows :
(i) Photons have particle characteristic. It is emitted or absorbed in units called quanta of light.
(ii) Photons have wave characteristic. It travels in space with particular frequency, a characteristic of waves.
(c) Three observed features which can be explained by this equation are :
(i) Solar cells : Also called photo-voltaic cells. It converts solar radiations to electrical emf.
(ii) Television telecast : The dark and bright light part of images are interpreted as high and low electrical charges as given by photoelectric emission principle. These are further processed and transmitted.
(iii) Burglar alarm : The moment the ultraviolet radiation is cut due to thief, it stops the supply of photons and thus work as "off" mode and the ring bells automatically.