REFRACTION Bending of Light Light slows down or
REFRACTION (Bending of Light) Light slows down or speeds up when it enters and leaves another material
• Pencil Demo
Refraction • The change in direction of a wave as is crosses the boundary between two media in which the wave travels at different speeds.
Index of Refraction
• Pyrex Demo
Dispersion is the refraction of white light into separate colours. Different colours of white light travel at different speeds (v) and have a different “n” value.
Index of Refraction Higher the index the slower the speed of light
Snell’s Law
Snell’s Law Towards the normal Away from the normal
The Critical Angle ( c) The Critical Angle is the angle where the light refracts along the boundary (sin 2 = 90 o).
Total Internal Reflection Using a refraction simulation, we can see why this is impossible. Total Internal Reflection occurs when light cannot refract but bounces back into the more dense medium.
If n 1 > n 2 • When light passes into a less optically dense medium, it moves away from the normal line. • At a large enough incident angle, light refracts at an angle of 90 degrees. . . • This is called the “critical angle”. • This is called “Total Internal Reflection”
Total Internal Reflection & the Critical Angle
• Fibre optics work by total internal reflection! Information, traveling in the form of light, is able to move around the Earth very fast using fibre optics.
Fibre Optics:
• Due to total internal reflection, you will see reflections of objects in water on the waterair boundary when viewed from inside the water.
Refraction Applications • • • Diamonds Fibre Optic Cables Binoculars and Periscopes (check out this video too) Rainbows Mirages
Mirages Explained
- Slides: 18