Q9Q Figure 33-32 shows four long hor... [FREE SOLUTION]

Chapter 33: Q9Q (page 1000)

Figure 33-32 shows four long horizontal layers 础鈥揇 of different materials, with air above and below them. The index of refraction of each material is given. Rays of light are sent into the left end of each layer as shown. In which layer is there the possibility of totally trapping the light in that layer so that, after many reflections, all the light reaches the right end of the layer?

Short Answer

Expert verified

The layer in which there is possibility of totally trapping the light so that, after many reflections, all the light reaches the right end of the layer is layer B.

Step by step solution

Given data

Figure 33-32 showing four horizontal layers A-D of different materials with their refractive indexes, with air above and below them is given.

Understanding the concept of total internal reflection

Using total internal reflection, a light source can be trapped with a medium. For a total reflection case, the refractive index of the medium having the light source needs to be greater than the refractive index of the medium outside or at the layer of the medium.

Calculation of the layer that is possible case of trapping of the light

A wave encountering a boundary across which the index of refraction decreases will get rapped totally means undergo total internal reflection.
So, the adjacent layers should have less refractive index than the layer in which light is incident to get it trapped totally.
In this case, this condition is satisfied by only layer B as both the materials at the sides of material B have refractive index lower than refractive index of B.
Therefore, the layer in which there is possibility of totally trapping the light so that, after many reflections, all the light reaches the right end of the layer is layer B.