If light travelling in a straight line bends by a small but fixed angle, it could be an instance of

Step-by-step solution

When light undergoes reflection, its path changes direction. For a given angle of incidence i , the angle of deviation is = 180^ - 2i . By choosing an appropriate angle of incidence (such as grazing incidence where i 90^ ), the deviation can be a small, fixed angle. When light undergoes refraction through a thin prism, it deviates by a small, fixed angle given by = ( - 1)A , where is the refractive index and A is the angle of the prism. Dispersion involves different wavelengths of light bending by different angles,