Question

In a plane electromagnetic wave if the amplitude of oscillating electric field is $45,Vm^{-1}$ then the amplitude of the oscillating magnetic field is

• A. $2.5\times10^{-8},T$
• B. $1.5\times10^{-7},T$
• C. $3\times10^{-8},T$
• D. $1.5\times10^{-8},T$
• E. $2.5\times10^{-7},T$

Hint:

Physics Tip: In EM waves, electric and magnetic fields are always perpendicular and related by $E=cB$.

Answer 1

The Correct Option is B

Concept:
For electromagnetic waves in vacuum: $$E_0=cB_0$$ where $E_0$ = electric field amplitude, $B_0$ = magnetic field amplitude, $c=3\times10^8,m/s$
Step 1: Use given values.
$$E_0=45,V/m$$ So, $$B_0=\frac{E_0}{c}$$
Step 2: Calculate magnetic field.
$$B_0=\frac{45}{3\times10^8}$$ $$=15\times10^{-8}$$ $$=1.5\times10^{-7},T$$
Step 3: Final answer.
Hence correct option is (B). :contentReference[oaicite:1]{index=1}