Physics » Electromagnetic Waves » Energy in Electromagnetic Waves

# Summarizing Energy in Electromagnetic Waves

## Energy in Electromagnetic Waves Summary

• The energy carried by any wave is proportional to its amplitude squared. For electromagnetic waves, this means intensity can be expressed as

$${I}_{\text{ave}}=\cfrac{{\mathrm{c\epsilon }}_{0}{E}_{0}^{2}}{2},$$

where $${I}_{\text{ave}}$$ is the average intensity in $${\text{W/m}}^{2}$$, and $${E}_{0}$$ is the maximum electric field strength of a continuous sinusoidal wave.

• This can also be expressed in terms of the maximum magnetic field strength $${B}_{0}$$ as

$${I}_{\text{ave}}=\cfrac{{\text{cB}}_{0}^{2}}{{2\mu }_{0}}$$

and in terms of both electric and magnetic fields as

$${I}_{\text{ave}}=\cfrac{{E}_{0}{B}_{0}}{{2\mu }_{0}}.$$

• The three expressions for $${I}_{\text{ave}}$$ are all equivalent.

## Glossary

### maximum field strength

the maximum amplitude an electromagnetic wave can reach, representing the maximum amount of electric force and/or magnetic flux that the wave can exert

### intensity

the power of an electric or magnetic field per unit area, for example, Watts per square meter

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