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Explain the inverse linear dependence of stopping potential on the incident wavelength in a photoelectric effect experiment.

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Question

Explain the inverse linear dependence of stopping potential on the incident wavelength in a photoelectric effect experiment.

Answer in Brief
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Solution

When a beam of light of a specific wavelength (or frequency) strikes the metal's surface, the total number of electrons ejected and the kinetic energy of each electron is given by,
K.Emax ​= `"hc"/lambda - phi,`
Where, V0​ is stopping potential.
So, `"V"_0"e" = "hc"/lambda - phi,`
where V0 is the stopping potential, e is the charge magnitude on the electron, h is Planck's constant, c is the speed of light in free space, λ is the wavelength of the electromagnetic radiation incident on a metal surface and Φ is the work function for the metal, h, c and e are constants. For a specific metal, Φ is constant.

Hence, it follows that as `1/lambda` increases, V0 increases.
The plot of V0 verses `1/lambda` is linear. This is due to the fact that the energy associated with a quantum of radiation (photon) is directly proportional to its frequency and thus inversely proportional to its wavelength of radiation.

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Chapter 14: Dual Nature of Radiation and Matter - Exercises [Page 322]

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Balbharati Physics [English] Standard 12 Maharashtra State Board
Chapter 14 Dual Nature of Radiation and Matter
Exercises | Q 3. | Page 322

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