Page 1 - Lesson note refractive index

SAI INTERNATIONAL SCHOOL
PHYSICS
CLASS X
Chapter: LIGHT(REFLECTION & REFRACTION)
MODULE-27

LESSON NOTES:

The Refractive Index
o We now know about refraction of light and the extent of the change in
direction that takes place in a given pair of media is expressed in terms
of the refractive index, the "constant" appearing in equation 1.
o The refractive index is related to an important physical quantity that is
relative speed of propagation of light in different media as light
propagates with different speeds in different media.
o Consider the figure given below

o Let v 1 be the speed of light in medium 1 and v 2 be the speed of light in
medium 2 then the refractive index of medium 2 with respect to
medium 1 is given by the ratio of the speed of light in medium 1 and
the speed of light in medium 2. So,

where n 21 is the refractive index of medium 2 with respect to medium 1.
o The refractive index of medium 1 with respect to medium 2 is
represented as n12. It is given by

1