Question

the refractive index of diamond is 2.42 what is the meaning of this statement

Answer 1

the ratio of speeds of light, in a given pair of media , gives us a measure of the extent of refraction (or bending) of a ray of light as it goes from one medium to another. this ratio is called relative refractive index.

relative refractive index of medium 2 in respect to medium 1

= speed of light in medium1/ speed of light in medium 2

absolute refractive index of a medium(m)

=speed of light in vaccum/speed of light in the given medium

so here the absolute refractive index of diamond is 2.42

Answer 2

The meaning of this statement is that

the speed of light in medium (say diamond) is 2.42