A) \[2.65\times {{10}^{6}}\text{ }m/s\]
B) \[7.02\times {{10}^{12}}\text{ }m/s\]
C) \[1.87\times {{10}^{6}}m/s\]
D) \[32\times {{10}^{-19}}m/s\]
Correct Answer: A
Solution :
Since,\[{{V}_{2}}>{{V}_{1}}\]so electric field will point from plate-2 to plate-1. The electron will experience an electric force, opposite to the direction of electric field and hence move towards the plate-2. Use work-energy theorem to find speed of electron when it strikes the plate -2. \[\frac{{{m}_{e}}{{v}^{2}}}{2}-0=e({{V}_{2}}-{{V}_{1}})\] \[(\because \Delta KE=W)\] where,\[{{m}_{e}}\]and are mass and charge respectively of the electron and v is the required speed. \[\therefore \] \[\frac{9.11\times {{10}^{-31}}}{2}{{v}^{2}}=1.6\times {{10}^{-19}}\times 20\] \[\Rightarrow \] \[v=\sqrt{\frac{1.6\times {{10}^{-19}}\times 40}{9.11\times {{10}^{-31}}}}\] \[=2.65\times {{10}^{6}}\,m/s\]You need to login to perform this action.
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