Modern Physics 2 Question 3

3. In a photoelectric effect experiment, the threshold wavelength of light is 380nm. If the wavelength of incident light is

260nm, the maximum kinetic energy of emitted electrons will be

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Answer:

Correct Answer: 3. (c)

Solution:

  1. Given, threshold wavelength, λ0=380nm

Wavelength of incident light, λ=260nm

Using Einstein’s relation of photoelectric effect,

(KE)max=eV0=hνhv0 But hν=E=1237λ(nm)eVE0=1237λ0(nm)eV

From Eqs. (i) and (ii), we get

(KE)max=EE01237λ1237λ0eV=12371λ1λ0eV(λ in nm )

By putting values of λ and λ0 in Eq. (iii), we get

(KE)max=123712601380eV=1237×380260380×260eV(KE)max=1.5eV



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