 Similar to the word "re-emission", it is the light which is scattered back from a material, as opposed to that which is "transmitted" through the material.The word "re-emission" connotes no such directional character.Based on the origin of the word "emit", meaning "to send out or away", "re-emit" means "to send out again", "transmit" means "to send across or through", and "remit" means "to send back".