A) \[1.6\times {{10}^{6}}\]
B) \[0.85\times {{10}^{6}}\]
C) \[0.425\times {{10}^{6}}\]
D) \[8.5\times {{10}^{6}}\]
Correct Answer: D
Solution :
: Force on electron in uniform electric field is \[F=eE\] The acceleration of the electron is \[a=\frac{F}{m}=\frac{eE}{m}\] where m is the mass of the electron. Starting from rest, the velocity of the electron when it has travelled distance s is \[\upsilon =\sqrt{2as}=\sqrt{2\frac{eE}{m}}s\] Here, \[\frac{e}{m}\simeq 1.8\times {{10}^{11}}Ck{{g}^{-1}}\] \[E=1\times {{10}^{4}}N{{C}^{-1}}\] \[s=2\times {{10}^{-2}}m\] \[\therefore \] \[\upsilon =\sqrt{2\times 1.8\times {{10}^{11}}\times 1\times {{10}^{4}}\times 2\times {{10}^{-2}}}\] \[=8.5\times {{10}^{6}}m{{s}^{-1}}\]
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