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

Hint:

In an electromagnetic wave, the electric and magnetic field strengths are related by the speed of light.

Answer 1

The Correct Option is B

Step 1: The relation between the electric field \( E \) and magnetic field \( B \) in an electromagnetic wave is given by: \[ E = cB, \] where \( c \) is the speed of light in vacuum, \( c = 3 \times 10^8 \, \text{m/s} \).
Step 2: Given \( B = 20 \, \text{nT} = 20 \times 10^{-9} \, \text{T} \), the electric field strength is: \[ E = 3 \times 10^8 \times 20 \times 10^{-9} = 6 \, \text{V/m}. \]
Final Answer: \[ \boxed{6 \, \text{V/m}} \]