(i) How does one explain the emission of electron from a photosensitive surface with te help of Einstein's photoelectric equation ?
(ii) The work function of the following metals is given : `Na = 2.75 eV, K = 2.3 eV, Mo = 4.17 eV` and `Ni = 5.15 eV`. Which of these metals will not cause photoelectric emission for radiation of wavelength `3300 Å` from a laser source placed 1 m aways from these metals ? What happens if the laser source is brought nearer and placed 50 cm away ?

Explanation

Identification of metals/s which does/do not cause photoelectric effect Photoelectric emission.
Effect produced
`E=(hv)/(lamda)=(6.63xx10^(-34)xx3xx10^(8))/(3.3xx10^(-7)xx1.6xx10^(-19))eV`
`=3.77eV`
The work function of Mo and Ni is more than the energy of the incident photons, so photo-electric emission wil not take place from these metals. Kinetic energy of photo electrons will not change, only photoelectric current will change.