1) A metal has a work function of 1.95 ev. a) If light of wavelength 5.2 x 10^-7

Question

1) A metal has a work function of 1.95 ev. a) If light of wavelength 5.2 x 10^-7 m is incident on its surface, will electrons be ejected through the photoelectric effect? Explain how you know. If so, at what speed will the fastest of them leave the metal surface? b) The fastest moving of the ejected electrons are generally those near the metal surface. Imagine an electron deeper in the same metal at a position where 2.1 ev?s of energy are required to leave the metal. Can an electron at that position still be ejected? Explain. If so, how much kinetic energy will it have as it leaves?

Explanation / Answer

to eject any electron, the energy of the light has to be greater than work function.

so energy of the light incident=h*c/wavelength

where h=planck's constant

c=speed of light

energy=2.389 eV

so it will be able to eject electron through photo electic effect.

energy of the ejected electron=2.389-1.95=0.439 eV

so if speed of the jected electron is v,

then 0.5*mass if electron*v^2=0.439 eV

v=3.929*10^5 m/s

b)as the energy of the incident light is 2.389 eV, the metal at 2.1 eV work function can eject electron.

its kinetci energy will be 2.389-2.1=0.289 eV

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