Dual Nature Of Radiation And Matter Ques 30
30. Two radiations of photons energies $1$ $ eV$ and $2.5 $ $eV$, successively illuminate a photosensitive metallic surface of work function $0.5$ $ eV$. The ratio of the maximum speeds of the emitted electrons is :
[2012 M]
(a) $1: 4$
(b) $1: 2$
(c) $1: 1$
(d) $1: 5$
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Answer:
Correct Answer: 30.(b)
Solution:
- (b) According to Einsten’s photoelectric effect, the K.E. of the radiated electrons
$K . E _{\max }=E-W$
$\frac{1}{2} m v_1^{2}=(1-0.5) eV=0.5 $ $eV$
$\frac{1}{2} m v_2^{2}=(2.5-0.5) eV=2$ $ eV$
$\frac{v_1}{v_2}=\sqrt{\frac{0.5}{2}}=\frac{1}{\sqrt{4}}=1: 2$
BETA
