Question

A beam of white light (containing frequencies ranging from 4.00 × 10¹⁴ Hz to         7.90 × 10¹⁴ Hz) is incident on a sodium surface, which has a work function of 2.28 eV.

a. What is the range of frequencies in this beam of light for which electrons are ejected from the sodium?

b. What is the maximum kinetic energy of the photoelectrons ejected from the sodium?

Answer:          (a) From 5.50 × 10¹⁴ Hz to 7.90 × 10¹⁴ Hz               (b) 1.59 × 10^-19 J

Answer 1

(a) The range of frequencies in the beam of light is f_o = w_o/h = (2.28 ev) (1.60 times 10^-19 J/ev)/6.63 times 10^-34 J.S = 5.50 times 10^14 HZ The ejectual frequency is 5.50 times 10^14 HZ to 7.90 times 10^14 HZ. (b) THe maximum kinetic energy is K_man = h_f - w_o = (6.63 time 10^-34) (7.9 times 10^14) - (2.28ev) times (1.6 times 10^-19 J/ev) 1.59 times 10^-19 J