Would casting this at a wraith be an effective defense?

Ideas:

- Use on ice (or something else that you can break), smash it all over the floor and you lit the place up.

- Cast Light (or Darkness) on a pin and use a grapple to pin it to an opponent

- Cast Light/Darkness on a coin and throw it down a hallway

Source: https://www.reddit.com/r/dndnext/comments/3x4rjq/no_cantrip_is_useless_examples_for_all_of_them 

- Light cast on an opponent who uses stealth or invisibility can stop them in their tracks as you make them or their equipment glow (they do get a save but this is often forgotten application) (Source: http://www.giantitp.com/forums/showthread.php?488397-Let-s-make-cantrips-fun-and-powerful-with-tricks-tips-and-combos) 

Is the firefly/moss consumed?

No, material components explicitly state when they are consumed.

So if I cast this on an enemy who needs to make a saving throw, if they fail will they become blinded? I don't fully understand.

Spellword is:  Invictus

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.

Quote from Intortus_ >>

So if I cast this on an enemy who needs to make a saving throw, if they fail will they become blinded? I don't fully understand.

 No, they make the saving throw to avoid the spell. Blindness/Deafness is a 2nd level spell which specifically causes the blind condition. Compare the spell descriptions of both spells to see how they are different.

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

As written there are two elements relevant to your question:

1) the object sheds bright light

2) Completely covering the object with something opaque blocks the light.

The first part says it is the entire brick that is shining, not just the part you touched. The secnd part says it requires a complete covering to block light but clearly the front and presumably the reverse are not covered.

So I would agree with you. It would in effect turn on a light on the far side of the wall since the object is light-ed and it is not completely covered. Of course, DM always has the final say.

Let's say I have a smoke bomb and i cast light on it. Does each little piece have a bit of light on it making it light up the room while still being opaque? 

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.

 Brick walls are usually two or three layers of bricks thick. It may not shine on the other side because there is a second layer of bricks on the other side?

 

 Brick walls are usually two or three layers of bricks thick. It may not shine on the other side because there is a second layer of bricks on the other side?

 I would assume it is just one layer of brick since the question doesn't involve extra layers, the question is simply trying to figure out if it would shine through the wall if the brick they are touching is also on the other side. 

Technically speaking, this evocation would not work on a brick of a wall, RAW states that the object must be no larger than 10 feet in any dimension.

A single brick, not attached to anything would make sense... however, a brick that has been bonded to other bricks with a mortar, is no longer a single brick. It is now a piece of a complete wall.

That being said, there would be nothing to prevent the oposit side of said beick from shining... as the entire brick would be eminating the light, not just one part of it, as said brick is a three dimensional object.

Intortus: They will just emit light. Keep in mind it's on an object as well

One of the best uses for light is to cast it on an arrow for and shoot it for long ranged scouting and disabling light sensitive foes like cloakers with a giant glowing pin stuck in them.

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.

 Brick walls that are 1 brick thick aren't walls; they're piles of rubble.

A little late on the reply, burning wouldnside with the DM.

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.

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 cannot cast this on an enemy, only on objects.