A friend emailed a photo to me that he said he took. Is there a way I
can see "embedded" info on this file that would let me know if he
copied it from a webpage or some similar method? Is there a way to
verify the source of this photo - or at least tell if it was copied
from another source?

This is not an answer, but a passing comment.
Unfortunately there is no sure method to tell if your friend took the
photo.
Their may be a chance if he 'borrowed' the photo that a digital
watermark may be embedded by the copyright holders, or perhaps there
might be some data in some EXIF header left by a digital camera, but
this is not always the case and with the ease of 'borrowing' images
from the internet it makes it more difficult.
regards
lot-ga

Few photos on Web pages are "watermarked."

One thing you might do is use Google Image Search to hunt for the
image on the Web, using appropriate keywords (if the photo is a
picture of a trout, search for "trout," if the photo is a picture of a
rose, search for "rose," just the obvious sorts of descriptive words
for this particular photo.)

Google Image Search
http://images.google.com/

Open the file as a text file.  If there is any text that you can read,
it will tell you the program or camera that created it...then quiz
your friend about which program or camera he used to make the picture.

One more thing to try:  identify the file name of the photo and then
do a google search for the full filename (use quotes, e.g.,
"rosephoto.jpg").  If it's out there on the web, and if the name
wasn't changed during downloading (if, in fact, it was downloaded!)
then you might come across it.