A) 100 sec
B) 25 sec
C) 50 sec
D) 75 sec
Correct Answer: C
Solution :
For equal fogging \[{{I}_{2}}\times {{t}_{2}}={{I}_{1}}\times {{t}_{1}}\] \[\Rightarrow \ \ \frac{{{L}_{2}}}{r_{2}^{2}}\times {{t}_{2}}=\frac{{{L}_{1}}}{r_{1}^{2}}\times {{t}_{1}}\]\[\Rightarrow \ \ \frac{16}{4}\times {{t}_{2}}=\frac{20}{1}\times 10\] \[\Rightarrow \ \ {{t}_{2}}=50\sec .\]
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