- #1

Blastrix91

- 25

- 0

## Homework Statement

When deriving the intensity of an electromagnetic wave in my textbook, there was a part I didn't quite get.

It's how I = Watts/m^2 becomes I= u c

My textbook gave an example of a electromagnetic wave through a cylinder, with cross-section area A. In 1 second it would have traveled length c. Now that makes sense.

It then proceed with changing the cross-section area with 1 and by that derives I= u c.. ? I don't get it.

## Homework Equations

I = Watts/m^2

I= u c

## The Attempt at a Solution

So can anybody help me conceptualise this derivation?