noun, noun or participle which takes 'suru'
reflection of sunlight
Refers specifically to the reflection of sunlight, often on water or other surfaces. Can be used as a noun or with する to describe the action of sunlight reflecting.
湖面に夕日が返照している。
The evening sun is reflecting off the lake surface.
窓ガラスの返照が眩しい。
The reflection of sunlight on the window glass is dazzling.
反射 is the general term for reflection (of light, sound, etc.), while 返照 is a more literary or specific term for the reflection of sunlight.
Compound of 返 (へん, 'return') and 照 (しょう, 'shine'). The exact historical derivation is uncertain, but the kanji suggest the idea of light shining back.