Triangular Prism Principle: sunlight is complex color light, there are red, orange, yellow, green, blue, indigo and violet these different frequencies of light. These for the same medium has a different refractive index, so a beam of light into the prism, the deflection angle of refraction (the law of refraction of light. The sine of the angle of incidence is proportional to the sine of the angle of refraction, and the coefficient of proportionality is the refractive index), so the beam of light that was originally going in one direction will be broken up into bands of light that are sequentially arranged according to the angle of deflection.

triple prism in life:
In clinical practice, the main treatments for nonadjustable strabismus are surgical correction and trismus correction. Parents have a load of questions about how to choose between these two treatments. For
non-adjustable childhood strabismus with a clear diagnosis, horizontal strabismus ≥15△ and vertical strabismus ≥10△ can be surgically corrected in principle. Especially for children whose binocular stereopsis is affected, early surgical correction can help to re-establish binocular vision.

However, prisms themselves have certain limitations, such as thick lenses, only a prescription of less than 7 △ on one eye, and distorted vision. These problems also limit the use of prisms in clinical practice.