Sodium metal used in photoelectric experiment, illuminated with light wavelength 420nm. Stopping potential is .65volts. a. What is sodium's work function? b. What wavelength would produce a stopping potential of 1.69V with the same setup?

Question

anonymous · Answer

The KE of the electron=exV (V=stopping potential, e=charge of electron=1.6/10^19 C)
From Einstein photoelectric equation
hc/l=work function + KE(l=wavelength of incident light,c=speed of        light,h=Planck's constant=6.62/10^32 Js)
b.
Say the required wavength is l'
Again
hc/l'=work function(known from above)+ex1.69