15. The Energy possessed by a body by virtue
of its position or state is called :

The Energy possessed by a body by virtue of its position or state is called Potential energy.

Mathematically potential energy can be written as,

Potential energy = mgh

Where 'm' represents mass of the body, 'g' represents gravity of the earth and 'h' represents height of body. Potential energy depends on the height, higher the hight from the surface of the earth, maximum will be the potential energy.

im not to sure what it is

waves moving from a fast medium to a slow medium will experience a reflection as light travels more slowly than red light. total internal reflection occurs when the critical angle is.