Question

The photoelectric effect demonstrates the quantized nature of light.

a) What is the kinetic energy and speed of an electron ejected from a Na surface with work function 2.28 eV when illuminated by light of wavelength i) 410 nm ii) 600 nm?

b) What is the critical frequency fo of incident light below which no electrons are ejected?

c) Sketch a graph of kinetic energy of the ejected electron vs. frequency of incident light for the photoelectric effect in sodium. Indicate the work function and critical frequency on your graph. What is the slope of the graph?

Answer 1

1) * solution work fonction = 2. 28 ev x, = 410 nm E = hranc - 6.62x1034 x 3X108 - 1-681619 x 410X10-9 - 3.03 ev KES TE-WF 3.03 -2.28 -0.75 v for velocity { mu? 0.75 X 1-6X10-19 ve 50-75 X106 x16-19 x2 9-4X10-31 = 0.51 x 10omis = 5.18106 mis COT 12 - - 6.62 X 10 34 x 3X108 = 1-681619 x 600X10-9 = 2:0 7 er so electrons would not be ejected out. critical Frequency. hro= 2.28 ev Vo = 2.2 8 x1,6 X1079 -0.349x10'5 6+62 810-4 3-44 xio' Hz for graph E/ work ho= be + Ek f→ Ek z hro - DE y = mx + c [m=n slope=h function