Dual Nature Of Radiation And Matter Ques 33
33. Light of two different frequencies whose photons have energies $1$ $ eV$ and $2.5$ $ eV$ respectively illuminate a metallic surface whose work function is $0.5$ $ eV$ successively. Ratio of maximum speeds of emitted electrons will be
[2011]
(a) $1: 4$
(b) $1: 2$
(c) $1: 1$
(d) $1: 5$
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Answer:
Correct Answer: 33.(b)
Solution:
- (b) The maximum kinetic energy of emitted electrons is given by
$K . E=\phi-\phi_0$
$K . E_1=1 $ $eV-0.5 $ $eV=0.5 $ $eV$
$K . E_2=2.5$ $ eV-0.5 $ $eV=2 $ $eV$
$\therefore \frac{K \cdot E_1}{K \cdot E_2}=\frac{0.5 eV}{2 eV}=\frac{1}{4}$
$\Rightarrow \frac{v_1}{v_2}=\sqrt{\frac{1}{4}}=\frac{1}{2}$
BETA
