If I cast light on a small pebble and placed it in a sealed, transparent glass jar would it emit light outside of the jar?
The reason I am asking is because the rules for areas of effects say:
A spell’s effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn’t included in the spell’s area. To block one of these imaginary lines, an obstruction must provide total cover.
That means that the jar (which provides total cover) would prevent anything outside of the jar from being in light's area of effect. So, it seems to me that the rules imply that nothing outside the jar would be illuminated.
This actually does have potential mechanical implications in the game as can be seen in this question: Can magical darkness affect a magical light source that is in a sealed container?.
Am I missing something here or is this just an example of the rules creating a nonsensical effect?
Best Answer
Because we are exploring line of effect, it is important to note what, exactly, the effect is. If the effect of light, for example, is to create light centered on the object, the transparent container blocks that light since it blocks line of effect via full cover. If, on the other hand, it makes the object glow brightly enough to emit that light, the effect is constrained on the object itself and the light is a desirable side effect, kind of like setting things on fire with a fireball. In that case, the light wouldn't be blocked by glass any more than torchlight would. The key to distinguishing this in the spell is the word "sheds."
I've checked the PHB. The only objects that shed bright light are also the sources of that light, whether it be the flame from produce flame or that of a candle. Light, therefore, makes an object glow and the light it sheds will go right through glass.
Darkness makes a similar distinction:
If you cast darkness on an object, the magical darkness is being emitted and will pass through glass, as counterintuitive as it sounds. If you cast the spell on an area, it would be blocked by glass.