Meaning of photonegative

pho•to•neg•a•tive

Pronunciation: (fō"tu-neg'u-tiv), [key]
— adj. Physics.
  1. pertaining to a substance, as selenium, having a conductivity that decreases upon absorption of electromagnetic radiation.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.