Question

Light falls on a photoelectric surface that has a work function of 2.90 eV. If the voltage required to stop the ejected electrons is 0.210 V, what is the wavelength of the incident radiation?

Answers

drwls
The energy provided by a photon is
e*(Work function) + e*(stopping voltage)
= (1.602*10^-19 C)*(3.11 J/C)
= 4.98*10^-19 joules

Set that equal to h*c/(wavelength) and solve for wavelength.

Wavelength = 6.62*10^-34*3.00*10^8/4.98*10^-19
= 3.99*10^-7 m = 399 nanometers (violet)

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