a
unit of
energy having both
particle and
wave behavior: it has no
charge or
mass but possesses momentum. The
energy of light, x - rays,
gamma rays, etc., is carried by
photons.
—PDC Volume 1 Approved Glossary, —PDC 2 Approved Glossary, —PDC Volume 3 Approved Glossary, —PDC Volume 5 Approved Glossary, —PDC Volume 4 Approved Glossary, —PDC Volume 7 Approved Glossary, —PDC Volume 8 Approved Glossary