The work function of the following metals is given : Na 2.75 ev, K = 2.3 eV, Mo = 4.17 eV and Ni = 5.15 eV. Which of these metals will not cause photoelectric emission for radiation of wavelength 3300 Å from a laser source placed 1 m away from these metals? What happens if the laser source is brought nearer and placed 50 cm away?

Solution

straight E space equals space hc over straight lambda space equals space fraction numerator 6.63 space straight x 10 to the power of negative 34 end exponent space straight x space 3 space straight x space 10 to the power of 8 over denominator 3.3 space straight x space 10 to the power of negative 7 end exponent space straight x 1.6 space straight x 10 to the power of negative 19 end exponent end fraction eV space equals space 3.77 space eV

The work function of Mo and Ni is more than the energy of the incident
photons; so photoelectric emission will not take place from these metals.
Kinetic energy of photo electrons will not change, only photoelectric current
will change.

Some More Questions From Wave Optics Chapter

Answer the following questions, which help you understand the difference between Thomson's model and Rutherford's model better.
Is the probability of backward scattering (i.e., scattering of α-particles at angles greater than 90°) predicted by Thomson's model much less, about the same, or much greater than that predicted by Rutherford's model?

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