it says in the spell description that you can though.

Can you cast Light on a living object?

Wedge a coin in the bottom of a scroll tube, cast the spell on the coin, and you've got a flashlight. Put the cap on the scroll tube to temporarily turn it off.

It has a dex save suggesting that something must be able to save.

something animated as it's a dex save

so if you consider your enemy an object then i guess you actually can

The 1974 1st edition basic rules allowed you to cast it on an opponent's eye and blind them for the duration of the spell. But that was soooooo over used that they took that away.

Quote from Edney >>

Would casting this at a wraith be an effective defense?

It depends on your DM. I tried it once and my DM ruled that the wraith had disadvantage on attack rolls for it's next turn, but I would say that it is not worth your action.

Would casting this on a friendly players armour be an acceptable way of getting light in a dark tunnel, or would that be too bright for the players to be used in this fashion? 

this would work fine. 

Quote from Skyraptor62 >>

Can you cast Light on a living object? 

 You can't target a creature, but you can target an object worn or carried by a creature. Unless by "living object" you mean something like a tree, which would not be considered a creature for rules purposes? In that case it could be the target as long as it's smaller than 10 feet.

no it would say so if it would

AoE question:

A)  Cast this on a coin.   Your effective radius is 20'... or 3.5 squares to either side, because the 5' square the coin is in consumes '0.5 squares' of radius.

B)  Cast this on a 5'x5' block.  Your effective radius is 22.5'... or 4 full squares to either side, because you fill the 5' square the block is in.

C)  Cast this on a 10'x10' block.  Your effective radius is 25'... or 5 full squares to either side, because you fill two 5' squares across the center.

Right?

Quote from Edney >>

Would casting this at a wraith be an effective defense?

 RAW says no, because this light isn't considered sunlight.  To activate Sunlight Sensitivity, you would need to cast dawn or sunbeam.    

This can illuminate the darkness spell.

Quote from Edney >>

Would casting this at a wraith be an effective defense?

 Yes, It would.

Quote from Nadolnt210 >>

So I have a question about how the spell works. I tried to cast this on a brick that was part of a wall, my DM said this was fine but said light would not end up on the other side of the brick because he sees the magic coming from your hand (touch spell), spreading around the objects surface and being stopped by the opaque objects around the brick (other bricks in the wall) and never making it to the other side... I interpreted this spell as you touch an object to infuse with magic, the whole object, emanating magic light from the center point of said object and just the sides that are blocked would not shed light but the front and back of the brick would since they are not covered... just looking for better clarity on this if there is any available or is this one of those whatever the DM wants to do type situations? Thanks for any help.

 It is only one target, or side.

Have I answered all your questions?

If a monster has Light Sensitivity, cast it on your melee characters weapon or armor.  If your frontline player is playing a melee character with the Sentinel Feat, you can effectively keep the enemy close to the light source.  This is also helpful on creatures with Shadow Stealth, as the bright light will prevent the creature from hiding.  It's generally better to cast the spell on the melee character, rather than the monster, because monsters with Shadow Stealth typically have a high Dexterity (to fuel their stealth checks they are going to be making frequently from hiding).        

Quote from Tesseract_ >>

Quote from Pissedpeon >>

Would this spell cause those with sensitivity to light to fight at disadvantage?  My DM says that Daylight would do this, but not the Light spell.

 

Depends on which exact trait you're talking about. Drow for example are only sensitive to sunlight. Neither the Light nor Daylight spells create sunlight, but Dawn, Sunbeam and Sunburst do. Some monsters, like Cloakers, are affected by any bright light though, so Light or Daylight would work on them (but Dancing Lights would not because it only creates dim light).

 You can also use this spell against creatures with Shadow Stealth.  Cast it on the frontline character, and you will prevent the monster from hiding.  The Shadow Stealth ability might be the sole feature keeping the monster aliving, as sneaky creature rely on remaining unseen, and tend to be squishy.   

Quote from Dissident_Ace >>

It has a dex save suggesting that something must be able to save.

something animated as it's a dex save

so if you consider your enemy an object then i guess you actually can

 I would just like to point out that to "consider your enemy an object" is a direct violation of the rules. Creatures are creatures, objects are objects, and the closest things to overlap that I can think of - but that still aren't, because there is no overlap - are (1) a corpse, which is considered an object, and (2) a tree, bush, fungus, or similar "living" thing, which is also an object.

Quote from Dungeonmaster001 >>

it says in the spell description that you can though.

 It says that you can cast it on something they're holding or wearing, not on them.

 I personally interpret their Dex save as moving the target object so that you can't touch it and thereby cast the spell on it.

Quote from Helmut_McQuack >>

Quote from Dissident_Ace >>

It has a dex save suggesting that something must be able to save.

something animated as it's a dex save

so if you consider your enemy an object then i guess you actually can

 I would just like to point out that to "consider your enemy an object" is a direct violation of the rules. Creatures are creatures, objects are objects, and the closest things to overlap that I can think of - but that still aren't, because there is no overlap - are (1) a corpse, which is considered an object, and (2) a tree, bush, fungus, or similar "living" thing, which is also an object.

Quote from Dungeonmaster001 >>

it says in the spell description that you can though.

 It says that you can cast it on something they're holding or wearing, not on them.

---

 I personally interpret their Dex save as moving the target object so that you can't touch it and thereby cast the spell on it.

 For what it's worth, I agree with this interpretation of how the Dex save applies.

Quote from davdwilliams >>

The 1974 1st edition basic rules allowed you to cast it on an opponent's eye and blind them for the duration of the spell. But that was soooooo over used that they took that away.

Using light to blind may have been a common tactic but it was not as overpowered as it would be to allow this effect for a cantrip today.  The economics of spell casting were quite different.  There were no cantrips at the time so it wasn't a spell you could cast endlessly for free.  Rather, you had a limited number of spells and once you were out you were done for.  Also, you couldn't re-cast a spell.  You had to memorize specifically what was in each slot and couldn't cast lower level spells using higher level slots.

I have been saved by this spell on numerous occasions. Definitely among the greatest, overall solid 7/10 for all spells, 10/10 for specific archetype.

Aasimars can cast Light as a racial ability.  Do they still need the components to do so?  I'm guessing no, but is there an official verdict somewhere I can cite?