The angle formed between a light ray striking a surface and an imaginary line called the "normal," which is perpendicular to that surface. In photography, understanding the angle of incidence is important for controlling reflections, glare, and light fall-off, particularly when working with reflective subjects, glass, or studio lighting setups. Correctly managing the angle of incidence allows photographers to enhance contrast, highlight texture, and achieve more accurate lighting effects in both still life and portrait photography.