Question:
The electric field intensity produced by the radiation coming from a $100 \mathrm{~W}$ bulb at a distance of $3 \mathrm{~m}$ is E. The electric field intensity produced by the radiation coming from $60 \mathrm{~W}$
at the same distance is $\sqrt{\frac{\mathrm{x}}{5}} \mathrm{E}$. Where the value of $x=$
Solution:
$\mathrm{c} \in_{0} \mathrm{E}^{2}=\frac{100}{4 \pi \times 3^{2}}$
$c \in_{0}\left(\sqrt{\frac{\mathrm{x}}{5}} \mathrm{E}\right)^{2}=\frac{60}{4 \pi \times 3^{2}}$
$\Rightarrow \frac{x}{5}=\frac{3}{5}$
$\Rightarrow x=3$
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