Everyone's familiar with the standard two slot toaster. You put two
slices of toast in, push the handle down, all the heating elements
come on, and after a while the toast pops up and both slices are
evenly browned on both sides.

If you put only one slice in you go thru the same steps, push the
handle down, all the heating elements come on and after a while the
toast pops up. But in my toaster when it pops up there is a
considerable difference in the amount of toasting done on one side of
the slice compared to the other.

Why the difference when only one slice is toasted?