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