A) \[4m\]
B) \[~5m\]
C) \[10m\]
D) \[20m\]
Correct Answer: C
Solution :
[c] \[40=10\log \frac{{{I}_{1}}}{{{I}_{0}}},\,\,\,\,\therefore \frac{{{I}_{1}}}{{{I}_{2}}}={{10}^{4}}\] and \[20=10\log \frac{{{I}_{2}}}{{{I}_{0}},}\,\,\therefore \frac{{{I}_{2}}}{{{I}_{0}}}={{10}^{2}}\,\,\therefore \frac{{{I}_{1}}}{{{I}_{2}}}=100\] Also \[\frac{{{I}_{1}}}{{{I}_{2}}}=100=\frac{r_{2}^{2}}{r_{1}^{2}}=\frac{r_{2}^{2}}{{{1}^{2}}}\,\,\,or\,\,\,{{r}_{2}}=10m.\]
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