In a photoelectric experiment, the collector plate is at 2.0 V with respect to the emitter plate made of copper '(phi = 4.5)'. The emitter is illuminated by a source of monochromatic light of wavelength 200nm. Find the minimum and maximum kinetic energy of the photoelectrons reaching the collector.

Explanation

Given ` phi = 4.5 eV , lambda = 200 nm`
Stopping Potential of energy
` = E - phi = hc / lambda - phi`
`= 1242 / 200 - 4.5 `
` = 6.21 -4.5 = 1.71 eV `
Minimum 1.7 V is necessary to stop the electron. The minimum `K.E. = 2eV ` Since the electric potential of 2V is required to accelerate the electron to reach to plates. The max. K.E.
` = ( 2 + 1.7 ) eV = 3.7 eV `