reflector; reflective plate
A flat or panel-like object that reflects light, heat, sound, or radio waves. Used in photography, traffic safety, heating, and technical contexts.
写真スタジオで反射板を使って光を調整した。
We adjusted the light using a reflector in the photo studio.
It is required by law to attach a reflector to the back of a bicycle.
Compound of 反射 (reflection) + 板 (board, plate).