Question

what is pyramid
tell me

Answer 1

When light traveling in an optically dense medium hits a boundary at a steep angle (larger than the critical angle for the boundary), the light is completely reflected. This is called total internal reflection. This effect is used in optical fibers to confine light in the core.

Answer 2

A pyramid is a structure whose outer surfaces are triangular and converge to a single point at the top, making the shape roughly a pyramid in the geometric sense.

The base of a pyramid can be trilateral, quadrilateral, or of any polygon shape.

As such, a pyramid has at least three outer triangular surfaces (at least four faces including the base).

The square pyramid, with a square base and four triangular outer surfaces, is a common version.