1. the angle that a ray entering a refracting medium makes with a line drawn perpendicular to the surface of this medium;
2. the angle that a ray striking a reflecting surface makes with a line perpendicular to this surface. Syn: incident angle.
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1. the angle that a ray entering a refracting medium makes with a line drawn perpendicular to the surface of this medium;
2. the angle that a ray striking a reflecting surface makes with a line perpendicular to this surface. Syn: incident angle.