Electromagnetic Waves Part 1

We know that,
Ue=‌

1

2

ε0E2....(1)
where, Ue= average energy density due to electric field,
ε0= electrical permittivity of free space
and E= electric field.
and Um=‌

B2

2µ0

.....(2)
where, Um= average energy density due to magnetic field, µ0= magnetic permeability of free space
and B= magnetic field.
Also, E=CB (∵C=‌

1

√µ0ε0

)
⇒‌‌E=‌

B

√µ0ε0

Put this value in Eq. (1), we get
Ue=‌

1

2

ε0×‌

1

µ0ε0

B2
⇒‌Ue=‌

B2

2µ0

⇒‌Ue=Um  [using Eq. (2)]