Dual Nature Of Light Question 295
Question: Mercury violet light $ (\lambda =4558{AA}) $ is falling on a photosensitive material $ (\varphi =2.5eV) $ . The speed of the ejected electrons is in $ m{{s}^{-1}} $ , about [AMU (Engg.) 1999]
Options:
A) $ 3\times 10^{5} $
B) $ K_{A}=K_{B}/2 $
C) $ 4\times 10^{4} $
D) $ 3.65\times 10^{7} $
Show Answer
Answer:
Correct Answer: B
Solution:
By using $ E=W_{0}+\frac{1}{2}mv_{\max }^{2} $ ; where $ E=\frac{12375}{4558}=2.71\ eV $
$ \Rightarrow 2.71\ eV=2.5\ eV+\frac{1}{2}\times 9.1\times {{10}^{-31}}\times v_{\max }^{2} $
$ \Rightarrow 0.21\times 1.6\times {{10}^{-19}}=\frac{1}{2}\times 9.1\times {{10}^{-31}}\times v_{\max }^{2} $
$ \Rightarrow {v_{\max }}=2.65\times 10^{5}\ m/s $
BETA
