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JEE Mains · Physics · STD 12 - 8. Electromagnetic waves
A point source of \(100\,W\) emits light with \(5 \%\) efficiency. At a distance of \(5\,m\) from the source, the intensity produced by the electric field component is :
- A \(\frac{1}{2 \pi} \frac{ W }{ m ^2}\)
- B \(\frac{1}{40 \pi} \frac{ W }{ m ^2}\)
- C \(\frac{1}{10 \pi} \frac{W}{ m ^2}\)
- D \(\frac{1}{20 \pi} \frac{ W }{ m ^2}\)
Answer & Solution
Correct Answer
(B) \(\frac{1}{40 \pi} \frac{ W }{ m ^2}\)
Step-by-step Solution
Detailed explanation
\(I _{ EF }=\frac{1}{2} \times \frac{5}{4 \pi \times 5^2}\) \(=\frac{1}{40 \pi}\,W / m ^2\)
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