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Question
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?
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Solution
λ=3300 Å =330 nm
Energy possessed by this wave = `(hc)/λ= 1240/330 = 3.76 eV`
As the work function of Mo and Ni is more than the energy in the wave, so in Mo and Ni no photoelectric emission will happen.
If laser source is brought near, no effect will be seen as the energy of the wave will still be same.
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