![...caused by relative motion between
the source of the wave and the observer.
...caused by relative motion between
the source of the wave and the observer.](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
...caused by relative motion between
the SOURCE of the wave and the observer.
The Big Bang Theory Season 1, Episode 6
![Leonard, it is a source of great pain
to me and my family...
Leonard, it is a source of great pain
to me and my family...](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
Leonard, it is a SOURCE of great pain
to me and my family...
The Big Bang Theory Season 4, Episode 18
![as a source of information
as a source of information](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
as a SOURCE of information
The Big Bang Theory Season 11, Episode 16
![I know that money can
be a source of friction
I know that money can
be a source of friction](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
I know that money can
be a SOURCE of friction
The Big Bang Theory Season 12, Episode 3
![But not so deep as to introduce
a new source of friction. But not so deep as to introduce
a new source of friction.](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
But not so deep as to introduce
a new SOURCE of friction."
The Big Bang Theory Season 2, Episode 5