Refraction The bending of light

Refraction (p.332-343) When light travels from one substance to another its speed changes. This speed change can cause a ray of light to change its direction (refract or bend) if the ray is at an angle to the surface.

Demonstration: Fast to slow: Slow to Fast: normal fast : AIR slow: WATER fast : AIR slow: WATER

Demonstration: Fast to slow: Slow to Fast: Toward the normal normal fast : AIR slow: WATER fast : AIR slow: WATER

Demonstration: Fast to slow: Slow to Fast: Toward the normal fast : AIR slow: WATER Away from the normal fast : AIR slow: WATER

Total Internal Reflection Sometimes when light is going from a slow to a fast medium it refracts so much it doesn't escape. (Prisms are used as mirrors = 99% reflected) E.g. Fibre optics 1 min 2 min

demo

Practical Applications: Fibre Optics

Practical Applications: Diamond Cut

Practical Applications: Reflectors Reflect light back in the direction it came from

Practical Applications: Binoculars contains four prisms whose job it is to produce a final upright image for the user

Practical Applications: Endoscope A tube that is passed into the body to observe the intestines or stomach. This contains glass fibres and light travels along it by total internal reflection!

Review (This has a lot of extra stuff) 10 min