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 $0.5 eV$ to $0.8 eV$. The work function of the metal is :
[2014]
(a) $0.65 eV$
(b) $1.0 eV$
(c) $1.3 eV$
(d) $1.5 eV$
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Answer:
Correct Answer: 29. (b)
Solution:
- (b) According to Einstein’s photoelectric equation, $h \nu=\phi_0+K _{\max }$
We have
$h \nu=\phi_0+0.5$
and $1.2 h v=\phi_0+0.8$
Therefore, from above two equations $\phi_0=1.0 eV$.
Work function $(\phi_0)$ 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.
