Question

The magnetic field in a travelling electromagnetic wave has a peak value of 20 nT. The peak value of electric field strength is

• A. 3 V/m
• B. 6 V/m
• C. 9 V/m
• D. 12 V/m

Answer 1

Answer: (B)

6 V/m

Answer 2

From question,
$B_{0} = 20\,nT = 20\times 10^{-9}T$
$\vec{E_{0}} = \vec{B_{0}} \times \vec{C}$
$\left|\vec{E_{0}}\right| = \left|\vec{B_{0}}\right|.\left|\vec{C}\right| = 20 \times 10^{-9} \times 3\times 10^{8} = 6\,V/m.$
($\because$ velocity of light in vacuum $C = 3 \times 10^{8} \,ms^{-1}$)