Ncert Exercises & Solutions

The electric field produced by the radiations coming from $100~\text{W}$ bulb at a $3~\text{m}$ distance is $E$ . The electric field intensity produced by the radiations coming from $50~\text{W}$ bulb at the same distance is:
1. $\dfrac{E}{2}$
2. $2E$
3. $\dfrac{E}{\sqrt2}$
4. $\sqrt2E$

Hint:

$P\propto E^2$

Step: Find the electric field intensity produced by radiation from

$50~\text{W}$ .
The intensity produced by the bulb is given by;

$I = \frac{P}{4\pi r^2}~~~...(1)$
The electric field intensity produced by radiation is given by;

$I = \frac{1}{2}\varepsilon_0E^2c~~~...(2)$
From equations

$(1)$ and

$(2)$ we get;

$P \propto E^2$

$\Rightarrow E \propto \sqrt{P}$

$\Rightarrow \frac{E_2}{E_1}= \sqrt{\frac{P_2}{P_1}}$

$\Rightarrow \frac{E_2}{E}= \sqrt{\frac{50}{100}}=\sqrt{\frac{1}{2}}$

$\Rightarrow E_2 = \frac{E}{\sqrt{2}}$
Hence, option (3) is the correct answer.

NEET Information

courses

Company

Botany Questions

Chemistry Questions

Physics Questions

Zoology Questions