Answer: 1.84* 10 ^15 electrones /s for 365 nm. Maximum energy kinetic, 0.4 eV.
0 electrons/s for 730 nm,
Explanation: In order to solve this problem we have to take into account the following relationship for the the power is laser beam.
Power= Energy/time so we can considerer a numeber electrons/time* energy of each photon the we have the power of photon flux given by:
P=n*hν where n is the number of electrons per second and h the Plack constant.
The phton energy is equal h*c/λ; where c is the speed of light
for λ = 365 nm we have E=1240/365 nm=3.4 eV ( 1eV=1.6 * 10^-19J)
so n= P/hν=1*10^-3/3.40 *1.6*10^-19 =1.84 * 10^15 electrons/s
The maximun kinetic energy of photolectrons is given by:
hν-W= Ek where W is the work function
then Ek=(3.4-3)eV= 0.4 eV
Finally, for the case of λ =730 nm, the energy for this photon is
E=1240/730=1.7 eV
so with this energy it is not possible to obtain any photoelectrons because this energy is lower that the work fuction for this material.
