Question

4. Explain the change in the stopping potential according to the angle of the polarizer axis in terms of the particle property of the light.

Answer 1

Answer: There is no change in stopping potential for an electron when we change the polarising angle of a polarizer.

This is because the polarizer does nothing but changes the intensity of light according to the relation I=I₀ Cos² where is the polarising angle and I₀ is the maximum intensity of light (intensity of the incident light).

. According to particle nature, intensity of light is precisely the number of photons in a beam of light. Therefore, in other words polariser reduces the number of photons when light passes through it.

Now, even if we throw light polarised by angle , the energy for a single photon is going to remain h, according to    einstein and only the number of photons are less as compared to the original light beam.

Since, the energy of a single photon is the same and photoelectric effect is the result of one-to-one particle collision (e^- and photon), the energy transferred to the electron is all the same as was before and only ejected electrons are less in number due to less number of photons.

   Part of that h energy which was transferred to the electron goes into combatting the energy with which the electron was    bound to the atom or the crystal (Work function) and the remaining takes form of the electron's kinetic energy, described by the famous equation ke = h- W_o       -----------------------------

As is visible from the equation, Kinetic energy of a photon is independent of the intensity of light( number of photons)    since it gets energy from collision from a single photon, the Potential of the electrode required to stop the electron (stopping potential) is again independent of intensity therefore independent of the polarising angle.

  V= ke/q= (h- W_o)/q :q --> charge on an electron

   extra note: electrons have different locations in a crystal, so some kinetic energy of electron might also be lost in reaching    the boundary of the crystal, but still, the electrons already at the boundary have maximum kinetic energy defined by the relation .