The atomic mass unit is 1/12 of an atom of carbon 12, and is a very small amount to represent in kilograms:
is atomic mass unit.
This is why the benefits of the atomic mass unit is that it makes the representation of atomic masses easier in terms of the simplicity of the numbers that are used to represent the masses. Also using the atomic mass unit it is easier to compare the masses of different atoms,These numbers would be very small and would require negative powers of 10 to represent them, so it is more convenient to use the atomic mass unit.
Geometrical optics, or ray optics, describes the propagation of light in terms of "rays" which travel in straight lines, and whose paths are governed by the laws of reflection and refraction at interfaces between different media.