What is the difference between the relative refractive index and the absolute?

The absolute refractive index is always greater than one, and the relative, depending on the direction of propagation of light, can be greater or less than one.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.