Answer: backscatter

AnswerCrossword Clue
backscatterLight from a flashgun or other light source that is deflected directly into a lens
backscatterthe deflection of radiation or particles by scattering through angles greater than 90 degrees with reference to the original direction of travel / to scatter in this way
backscatterDeflection of radiation or particles through an angle of 180░
backscatterRadiation or particles that have been deflected in this way