Dual Nature of Radiation and Matter - Result Question 27

29. When the energy of the incident radiation is increased by 20, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5eV to 0.8eV. The work function of the metal is :

[2014]

(a) 0.65eV

(b) 1.0eV

(c) 1.3eV

(d) 1.5eV

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Answer:

Correct Answer: 29. (b)

Solution:

  1. (b) According to Einstein’s photoelectric equation, hν=ϕ0+Kmax

We have

hν=ϕ0+0.5

and 1.2hv=ϕ0+0.8

Therefore, from above two equations ϕ0=1.0eV.

Work function (ϕ0) varies from metal to metal. The material is better for photoelectric emission whose work function is least. As caesium has least work function, hence it is best metal for photoelectric emission.



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