Coupon Accepted Successfully!


Refractive Index

The ratio Description: 82839.png, which is a constant, is called the relative refractive index of the refracting medium (2) with respect to the incident medium (1). It is also represented as 1μ2. Thus,
Description: 82849.png
In terms of the velocity of light for a given pair of media the refractive index is defined as
Description: 82868.png

i.e., Description: 82879.png
If μ1 and μ2 represent the refractive indices of the incident and refracting medium with respect to air, then
Description: 82990.png

Lateral Shift

Consider a parallel-sided glass slab ABCD of thickness t surrounded by a homogenous medium (air) as shown in Figure 9.20. IO is the incident ray, OR is the refracted ray and RE is the emergent ray. The emergent ray is parallel to the incident ray. RP is the sideward shift or lateral shift suffered by the incident ray IO in the glass slab.

The perpendicular distance between the incident ray and the emergent ray is called the lateral shift of the ray. It can be calculated using the formula
Description: 82999.png

where t is the thickness of the glass slab, i is the angle of incidence and r is the angle of refraction.
Description: Description: 88325.png

Fig. 9.20 Lateral Shift

Normal Shift

The floor of a swimming pool appears to be nearer, than it really is, to an observer on the diving board. This is a consequence of refraction when the observation is made normal to the refracting surface. This is called normal shift.
Normal shift is defined as that vertical distance through which an object appears to be shifted when an object placed in one medium is seen from another medium, observation being made normal to the surface separating the two media.


Description: Description: 88360.png
Fig. 9.21 Normal Shift


Using Snell’s law for small angles of incidence, it can be shown that the normal shift is given by the formula:
Description: 83006.png
where Sn is the normal shift, t is the thickness of the medium from the refracting surface to the object and rμd is the refractive index of denser medium with respect to the rarer medium.
It can also be shown that the refractive index Description: 83014.png

Test Your Skills Now!
Take a Quiz now
Reviewer Name