A laser delivers pulses of monochromatic light of wavelength
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A laser delivers pulses of monochromatic light of wavelength 500nm, each pulse lasting 10ns and carrying an energy of 1.5μJ. The pulses fall normally on a photoemissive surface of area 0.20cm2 whose quantum efficiency is 15% for this wavelength. Assume that all emitted electrons are collected instantaneously.
(i) Calculate the average power of one laser pulse.
(ii) Find the number of photons present in a single pulse.
(iii) Determine the total charge liberated from the surface during one pulse.
(iv) Hence compute the average photocurrent during the pulse duration and state its value in mA."