Provided the prism is constructed from a material having a refractive index greater than the square root of 2 (approximately 1.414), the light will undergo total internal reflection at the glass/air boundary while inside the prism. In a right-angle prism, a parallel bundle of light waves entering one of the smaller prism faces (or legs) at a perpendicular angle is reflected from the hypotenuse (longest) face and exits through the other leg.

The Orientation Mark slider can be utilized to rotate the orientation mark by any angle between zero and 360 degrees around the central axis. To operate the tutorial, use the Prism Orientation slider to change the orientation between a Right-Angle Prism, Porro Prism, or Dove Prism. Inversion, rotation, and reversion of the orientation mark can occur as a result of light passing through a right-angle prism, and is dependent upon the prism orientation. Light emitted by the orientation mark and reflected by the prism is represented by a single red line in the tutorial. The orientation mark contains a red sphere at the top, a blue block on the left arm, a stub at the bottom, and a yellow cone on the right arm. The tutorial initializes with the right-angle prism positioned to act as a Porro prism with light emitted from an orientation mark entering the hypotenuse face. This interactive tutorial explores light reflection and image rotation, inversion, and reversion by a right-angle prism as a function of the prism orientation with respect to incident light. The right-angle prism possesses the simple geometry of a 45-degree right triangle (see Figure 1), and is one of the most commonly used prisms for redirecting light and rotating images.

Right angle triangular prism calculator