File:Triplet prism with refraction angles.svg

Summary
A triplet prism, showing the apex angles ($$\alpha_1$$, $$\alpha_2$$, and $$\alpha_3$$) of the three elements, and the angles of incidence $$\theta_i$$ and refraction $$\theta'_i$$ at each interface. The deviation angle of the ray transmitted by the prism is shown as $$\delta$$.