This configuration is known as the " angle of minimum deviation ", and is easier to align than arbitrary angles.
2.
The deviation angle at this point is called the " minimum deviation " angle, or " angle of minimum deviation ".
3.
The angle of minimum deviation is attained when the angle of incidence and angle of emergence for a ray of light being refracted through a prism, are equal.
4.
The angle of minimum deviation is almost 22?( or more specifically 21.84?on average; 21.54?for red light and 22.37?for blue light ).