JEE Main 201412 AprilOnline
- Exam
- JEE Main
- Year
- 2014
- Date
- 12 April
- Mode
- Online
- Subject
- Physics
- Chapter
- Electromagnetic Waves
JEE Main 2014 · 12 April · Online · Physics · Electromagnetic Waves
A lamp emits monochromatic green light uniformly in all directions....
A lamp emits monochromatic green light uniformly in all directions. The lamp is efficient in converting electrical power to electromagnetic waves and consumes of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of from the lamp will be nearly:
Options
- A
- B
- C
- D
Correct answer
B.
Step-by-step solution
Wavelength of monochromatic green light
Now, half of this intensity (I) belongs to electric field and half of that to magnetic field, therefore,
\begin{aligned} \frac{\mathrm{I}}{2}=\frac{1}{4} \varepsilon_0 \mathrm{E}}_{0}^2 \mathrm{C}\\
&\text{ or } \mathrm{E}}_{0}=\sqrt{\frac{2 \mathrm{I}}{\varepsilon_0 \mathrm{C}}}
\end{aligned}\begin{aligned}&=\sqrt{\frac{2 \times\left(\frac{3}{100} \pi\right)}{\left(\frac{1}{4 \pi \times 9 \times 10^9}\right) \times\left(3 \times 10^8\right.}}\\
&=\sqrt{\frac{6}{25} \times 30}=\sqrt{7.2}\\
&\therefore \mathrm{E}}_{0}=2.68 \mathrm{ V}/ \mathrm{m}
\end{aligned}$