Question

In an electromagnetic wave, the energy density associated with the electric field will be:

• A. $\frac{1}{2}C{V}^2$
• B. $\frac{1}{2}\frac{q^2}{C}$
• C. $\frac{1}{2}\frac{{\epsilon }^2}{E}$
• D. $\frac{1}{2}{\epsilon }_0{E}^2$

Answer 1

Answer: (D)

$\frac{1}{2}{\epsilon }_0{E}^2$

Energy density due to electric field=$\frac{1}{2}ϵE^2$

Energy density due to magnetic field=$\frac{1}{2}\frac{B^2}{\mu }$

Since $\frac{E}{B}=c=\frac{1}{\sqrt{ϵ\mu }}$

Energy density is equally contributed to by electric and magnetic fields.