1. Applications of Reflected and Refracted Light
Chapter 17-2
Applications of Reflected and Refracted Light

2. Total Internal Reflection
Only occurs when light passes from more optically dense to less optically dense medium
Angle of incidence is so great that there is no refracted ray
All light reflects back into the incident medium

3. Total Internal Reflection and Critical Angle

4. Total Internal Reflection and Critical Angle
The angle at which the refracted ray, the “critical ray,” lies along the boundary
Can be calculated for all sets of materials from Snell’s Law:
Let θr = 90º

5. Example Problems:
What is the critical angle for crown glass in air? (Ans: 41.1º)
What is the critical angle for crown glass in water? (see p 397 for n)

6. Effects of Refraction
Optical Fibers (fiber optics):

7. Mirages: Caused by differences in n for hot air/cold air
Light is bent away from normal because n is less for hot air than cold air
Light seen is light from the sky refracted through the different temperature layers of air

8. Mirages: Light is refracted in air of different densities
Producing an effect similar to the light reflected off a pool of water

9. Mirages:
After the sun has set, it is still visible because refraction of light occurs over the horizon through the atmosphere

10. Dispersion of Light
Dispersion is the separating of light into its spectrum.
Light will disperse more (bend more toward the normal) in a medium with a higher index of refraction.

11. Newton’s Sketch of his demonstration of Dispersion:

12. Rainbows:
a spectrum formed when sunlight is dispersed by water droplets in the atmosphere. Violet seen on the inner arch of the rainbow and red on the outer.
Violet bends the most (and has the highest index of refraction).
Red bends the least (and has the lowest index of refraction).
Each color is refracted at a slightly different angle (red at 42° and violet at 40°).
A faint second order rainbow is caused by internal reflection as well as refraction.
Order of colors is reversed in the second order rainbow because of reflection

13. Rainbows:

14. Second Order Rainbow:
A second order rainbow is produced by light reflected twice inside the drop:
Note that order
of colors is
reversed

15. Second Order Rainbow:
Note that the order of colors is reversed

16. End 17-2