PYQ NEET- Electromagnetic Waves L-9

Question: In an electromagnetic wave in free space that root mean square value of the electric field is $E_{r m s}=6 \mathrm{~V} \mathrm{~m}^{-1}$. The peak value of the magnetic field is (NEET-2017)#

A) $2.83 \times 10^{-8} \mathrm{~T}$

B) $0.70 \times 10^{-8} \mathrm{~T}$

C) $4.23 \times 10^{-8} \mathrm{~T}$

D) $1.41 \times 10^{-8} \mathrm{~T}$

Answer: $2.83 \times 10^{-8} \mathrm{~T}$#

Explanation#

The rms value of magnetic field

$\mathrm{B}{\mathrm{rms}}=\frac{E{r m s}}{c}=\frac{6}{\left(3 \times 10^8\right)}=2 \times 10^{-8} \mathrm{~T}$

Now peak value of magnetic field

$\mathrm{B}{\text {peak }}=\sqrt{2} B{r m s}=2.83 \times 10^{-8} \mathrm{~T}$