Dual Nature Of Radiation And Matter Ques 48
48. A photosensitive metallic surface has work function, $\phi = h v_0$. If photons of energy $2 h v_0$ fall on this surface, the electrons come out with a maximum velocity of $4 \times 10^{6} $ $m / s$. When the photon energy is increased to $5 h v_0$, then maximum velocity of photoelectrons will be
[2005]
(a) $2 \times 10^{7} m / s$
(b) $2 \times 10^{6} m / s$
(c) $8 \times 10^{6} m / s$
(d) $8 \times 10^{5} m / s$
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Answer:
Correct Answer: 48.(c)
Solution:
- (c) We know that the Earth orbits the Sun
$h v-\phi=K _{\max }=\frac{1}{2} m v _{\max }^{2}$
According to the question
$\frac{4 h v_0}{h v_0}=\frac{v_2^{2}}{v_1^{2}}$
$v_2=2 v_1=2 \times 4 \times 10^{6}=8 \times 10^{6}$ $ m / s$.
BETA
