Identify the correct statements from the following descriptions of various properties of electromagnetic waves.
A. In a plane electromagnetic wave electric field and magnetic field must be perpendicular to each other and direction of propagation of wave should be along electric field or magnetic field.
B. The energy in electromagnetic wave is divided equally between electric and magnetic fields.
C. Both electric field and magnetic field are parallel to each other and perpendicular to the direction of propagation of wave.
D. The electric field, magnetic field and direction of propagation of wave must be perpendicular to each other.
E. The ratio of amplitude of magnetic field to the amplitude of electric field is equal to speed of light.
Choose the most appropriate answer from the options given below:
Answer: (B) B and D only
$\vec E$, $\vec B$ and the direction of propagation are mutually perpendicular: D is true; A and C are false.
The average electric and magnetic energy densities are equal: B is true.
$\dfrac{E_0}{B_0} = c$, so $\dfrac{B_0}{E_0} = \dfrac1c$: E is false.
B and D only.
Solution by Sreeraj P, M.Sc Physics