Depends on the spell and the light. Once Thorn gets within 20' with the torch you can see, but until then the 20% miss chance applies. Other than that it is all about your speed and the range of the spell.
I did so, and edited the IC results into the post below [# 637], also editing the gray OOC portion of the post with the IC results for each roll, but I didn't add my caster level to the SR rolls. That's done in the post below, but not in the OOC portion. It's below the red/orange IC rolls in white.
Added an initiative roll below [# 637], too. Banaq's init.=21.
Banaq's spell, magic missile, has a range of 160 feet, which is probably further out than he can see the target(s). So.... as soon as he can see them well enough to tell who's a good guy and who's a bad guy, he'll stop and blast 'em.
OOC:
I'm totally willing to take the damage and SR rolls that I've already made.