# For an electromagnetic wave travelling in free space,

Question:

For an electromagnetic wave travelling in free space, the relation between average energy densities due to electric $\left(\mathrm{U}_{\mathrm{e}}\right)$ and magnetic $\left(\mathrm{U}_{\mathrm{m}}\right)$ fields is :

1. (1) $U_{e}=U_{m}$

2. (2) $U_{e}>U_{m}$

3. (3) $\mathrm{U}_{\mathrm{e}}<\mathrm{U}_{\mathrm{m}}$

4. (4) $\mathrm{U}_{\mathrm{e}} \neq \mathrm{U}_{\mathrm{m}}$

Correct Option: 1

Solution:

(1)

In EMW, Average energy density due to electric $\left(\mathrm{U}_{\mathrm{e}}\right)$ and magnetic $\left(\mathrm{U}_{\mathrm{m}}\right)$

fields is same.