A Light spell cast at a Nogra will be absorbed (if the creature misses its saving throw) and have no apparent effect, but the energy of the spell will do 1-4 points of damage to the creature. Continual Light has the same properties, except that it can cause 2-8 points of damage if absorbed.
Light and Continual Light spells which are cast directly at a Nogra and not absorbed will simply dissipate. If either type of spell is cast in proximity to Nogra, with the intention of illuminating the area, the Nogra must be checked to see if they retreat as per the procedure above.