Question

Intensity of sunlight is observed as $0.092\, Wm ^{-2}$ at a point in free space. What will be the peak value of magnetic field at that point? $\left(\varepsilon_{0}=8.85 \times 10^{-12} C^{2} N^{-1} m^{-2}\right)$

• A. $2.77 \times 10^{-8} T$
• B. $1.96 \times 10^{-8} T$
• C. $8.31 \,T$
• D. $5.88 \,T$

Answer 1

Answer: (A)

$I_{\text {avg }}=\frac{B_{0}{ }^{2} C}{2 \mu_{0}} \& \frac{1}{\mu_{0}}=\epsilon_{0} C^{2}$
$I=\frac{B_{0}{ }^{2}}{2} \in_{0} C^{3}$
$B_{0}=\sqrt{\frac{2 I}{\epsilon_{0} C^{3}}}$
$B_{0}=2.77 \times 10^{-8} T$