TOTAL INTERNAL REFLECTION

1. TOTAL INTERNAL REFLECTION

2. Critical Angle • When light travels from a “slow” to “fast” medium: • As the angle of incidence increases, the angle of refraction continues to increase and bend away from the normal • When the angle of refraction reaches 90 degrees, the angle of incidence is called the CRITICAL ANGLE • This is a characteristic physical property of all mediums

3. Critical Angle

4. Internal Reflection • When a light ray reaches the critical angle, the angle of refraction is always at 90 degrees • If the angle of incidence reaches past the critical angle, the refracted ray will be reflected back into the medium • Refracted ray disappears and only a reflected ray is visible within the medium  TOTAL INTERNAL REFLECTION

5. Total Internal Reflection • http://www.youtube.com/watch?v=s7w1Z1FCgwA&feature=related

6. Total Internal Reflection 2 conditions for total internal reflection to take place: • Light has to travel from a slow  fast medium • The angle of incidence has to be greater than the critical angle (no refraction occurs)

7. Diamond • Diamonds sparkle due to the following: • The cut • High Index of refraction  small critical angle (24.4 degrees) • Results in a lot of total internal reflection for all incident rays entering the diamond • The sparkle is caused by the light bouncing off different sides of the diamond

8. Fibre Optics • Technology in which light is used to transmit information along a glass cable • Used in phones, computers and in medicine • The light entering this medium must not escape as it travels along the cable • The cable must have a high index of refraction