1. Total Internal Reflection

2. Refraction
Light moving from one medium to another will bend towards or away from the normal, depending on the speed of light in the second medium.

3. Total Internal Reflection

4. Critical Angle
The angle of incidence that produces an angle of refraction equal to
90 degrees.
Angle of refraction
Angle of
incidence

5. Total internal reflection occurs when the incident ray is greater than the critical angle

6. Why do you see the reflection?

7. Fibre Optic Cable

8. Critical Angle
If the angle of refraction is 90 degrees then light will travel along the surface of the two mediums.
Total internal reflection occurs when the angle of incidence is equal to or greater than the critical angle.

9. Total Internal Reflection
If the angle of incidence exceeds the angle of refraction, the refracted ray will not exit the first medium.
Rays reflect back
into the same
medium.

10. Total Internal Reflection
Light is traveling more slowly in the first medium than the second medium.
This means that the first medium has the largest index of refraction.

11. Total Internal Reflection
The angle of incidence is large enough that no refraction occurs in the second medium. The ray gets reflected back into the first medium which occurs if the angle of incidence is equal to or greater than the critical angle.

12. Comparison of Angles of Refraction

13. Use of Internal Reflection
Diamonds.
Diamonds have the highest index of refraction, but can increase the amount of total internal reflection by being cut properly making diamond sparkle.

14. Use of Internal Reflection
Fibre Optics.
Light transmits information along a high purity
glass or
plastic cable.

15. Fibre Optics The cable has a small critical angle.
Bouncing light will always have an angle of incidence greater than the critical angle and thus stay within the cable.

16. Fibre Optics Uses Communications – phones, communications, TVs
Movie Industry
Car dashboard lights
Medical Industry –
laparoscope surgery
Endoscope

17. Glass Prisms Critical incidence of 41.1°.
Reflect more than mirrors → mirrors absorb some light.
Silver backing of mirrors deteriorates.

18. Glass Prism Design

19. Periscopes

20. Binoculars

21. Retro-reflectors
Returns any light hitting it straight back towards the direction which it came from.
the corner of a glass cubes are used on many road signs to make them more noticeable.

22. Retro Reflectors
A and B are corner cube reflectors. C is a corner cube retro-reflector after three corners have been ground down.

23. Other uses – bicycle reflectors.

24. Total Internal Reflection
Vocabulary
Critical Angle
Total Internal Reflection
Fibre
Retro-reflectors
Homework
Pg. 531 # 1 – 6, 8