A) 4m
B) 5m
C) 10m
D) 20m
Correct Answer: C
Solution :
\[v=v{{\left( \frac{4}{3} \right)}^{1/2}}\] where \[A=4\pi {{r}^{2}}\] Since, \[40\,=10\,{{\log }_{10}}\,\left[ \frac{{{I}_{1}}}{{{I}_{0}}} \right]\] \[\frac{\Delta A}{A}=\frac{2\Delta r}{r}\] \[\frac{\Delta A}{A}\times 100=2\times 0.3%=0.6%\] Also, \[\frac{\Delta A}{A}=\frac{4\Delta r}{r}\] \[\eta =\frac{output\,power}{input\,power}\] \[=eI=\frac{e(E-e)}{R}\] \[\frac{d}{de}\left[ \frac{e(E-e)}{R} \right]=0\] \[\Rightarrow \] \[e=\frac{E}{2}\] \[\frac{1}{\lambda }=R\left[ \frac{1}{{{2}^{2}}}-\frac{1}{{{n}^{2}}} \right],\] \[n=3,4,5.....\] \[\frac{1}{{{\lambda }_{\max }}}=R\left[ \frac{1}{{{2}^{2}}}-\frac{1}{{{3}^{2}}} \right]\]
You need to login to perform this action.
You will be redirected in
3 sec
