Electromagnetic “Discontinuities” Must Propagate at a speed

Our wavefront satisfies both “Gauss’s laws” because there is no enclosed charge or current, and fields on opposite sides of the box are the same.

There is a changing B flux as the wavefront moves by. This changing flux must be equal to the line integral of the E field. Only the back edge (gh) contributes to this line integral.

There is a changing E flux also. This gives another reqd relation between E and B.

Accelerating Charges Radiate

Accelerating Charges Radiate

Coulomb’s law can’t describe the “kinked” E field. We got it from connecting field lines + geometry. However, we do get the kinked field if we consider the “potential”. “Potential” depends only on where the charge was and how fast it was moving a time r/c ago. (In other words, we have to account for the light travel time.) (we will need to do better than just the scalar electric potential, though)

But what’s it good for? Demos

Quiz: What are you doing this summer (3 pts for any answer): A] Maybe a physics problem a week or so, just to stay in top mental condition B] I won’t pick up a physics book C] I will use my expertise from Physics 161 to re- animate dead tissue.