Review of Reflection and Refraction of Light

1. Review of Reflection and Refraction of Light Finchum Physics 2013

2. Reflection of Light • Reflection = Bouncing • Occurs when medium is opaque • Angle of incidence is equal to angle of reflection. • All angles occur with respect to (wrt) the normal (perpendicular)

3. Refraction of Light • Refraction = bending • Occurs when the light wave is absorbed. • Angle of refraction is dependent on speed of refracted ray. • Speed of refracted ray is dependent on the index of refraction of the medium.

4. Index of Refraction • n • No units! • Equals the speed of light in a vacuum over the speed of light in the new medium. Higher “n”  Less speed - light bends toward the normal (less to more, toward) Lower “n”  more speed  light bends away from the normal (big to little  away, BLA)

5. Total Internal Reflection

6. Total Internal Reflection • Light travels in a medium and bends so much that it is totally internally reflected. • Occurs when: 1. internal medium has higher refractive index than external medium and 2. angle of incidence exceeds the critical angle

7. Example: TIR

8. Think about it

9. What do you see? • As the angle of incidence is greater, the amount of light refracted decreases and the amount of light reflected increases. • There is a point where all of the light reflects (that is Total Internal Reflection). • This occurs at the critical angle.

10. Where can we see this? • Fiber optic cables for communication – light travels faster than, say, electricity. • Also used in micro-surgeries. • Since all light is internally reflected, no energy is lost to the environment.

11. How do we know what the critical angle is? • It is dependent on the two media! • It also assumes that the angle of refraction is 90ᵒ.