Photoelectric effect is a phenomenon of emission of electrons from the surfaces of a metal when the light of suitable frequency falls on it. If light of frequency v falls on a photosenstive surface of work function `phi_(0)`, then the maximum kinetic energy of photoelectron emitted is given by Einstein's photoelectric equation.
`(KE)_(max)=1/2mv_(max)^(2)=hv-phi_(0)`
The value `(KE)_(max)` will increases if the energy of the incident light (hv) increases of work function `(phi_(0))` is decreased. Read above passage and answer the following questions:
(i) Why can visible light not ejected photoelectrons from every surface?
(ii) Light of frequency `7.21xx10^(14)Hz` is incident on a metal surface. Electrons with a maximum speed of `6.0xx10^(5)ms^(-1)` are ejected from the surface. What is the threshold frequency for photo emission of electrons? `h=6.6xx10^(-34)Js, m_(e)=9.1xx10^(-31)kg`.
(iii) What do you learn basically from the above study?