You draw energy from a light source, creating a ball of pure sunlight in your hands. If this spell absorbs light from the sun, convert all fire damage to radiant damage. This creates a sphere of bright light centered on the caster out to a range of 20 feet and dim light out to an additional 20 feet. This light that is produced is considered sunlight, even if the light was taken from a source that is not sunlight. Once cast, the caster may choose to either release it immediately or wait a turn or more to charge it. When charging, the caster cannot be hit or will lose focus on the spell, causing it to reduce its potency back to the uncharged version. The caster may hold the charge for up to a minute, after which the caster must release the spell or waste the spell slot used to cast. Once released, a 100 foot long, 5 feet wide line of pure sunlight shoots out from your hands and any creature in the line must make a Strength saving throw or take 4d8 fire damage (uncharged) and half as much on a successful save. If the spell is charged, the spell deals an additional 2d8 fire damage on top of the initial damage. 

Restriction: Spell cannot be cast in darkness, or if there is no source of light available.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the initial damage increases by 1d8 for each slot level above 3rd.