1. Refraction
Optical Phenomena

2. Total Internal Reflection
Total internal reflection – the complete reflection of light at the boundary of two transparent media; this effect occurs when the angle of incidence exceeds the critical angle
No light passes through the boundary
Critical angle – the minimum angle of incidence for which total internal reflection occurs
Light will travel parallel to the boundary
Can only occur when moving to a medium with a lower index of refraction
ni>nr
Used in fiber optics because almost no light intensity is lost
Sinθc = nr/ni
Sine of the critical angle = (index of refraction of the second medium) / (index of refraction of the first medium)

3. Total Internal Reflection

4. Atmospheric Refraction
Atmospheric refraction allows us to see while the sun is below the horizon
Before sunrise and after sunset
Mirages are observed when the air at ground level is much hotter than the air above it
Since gases have different densities based on temperature, they have different indices of refraction based on temperature
This produces both a real and a virtual image at the same point

5. Atmospheric Refraction

6. Dispersion
Dispersion – the process of separating polychromatic light into its component wavelengths
Using a prism to view the color spectrum
Violet light refracts the most
Red light refracts the least
When water droplets in the atmosphere cause dispersion and that light is totally internally reflected, a rainbow is visible

7. Dispersion

8. Dispersion

9. Lens Aberrations
Imperfections in the lenses cause aberrations so all rays are not focused at the focal point
Most common are spherical and chromatic aberration
Spherical aberration – the rays at the edges of the lens have a different focal length than rays near the center
Chromatic aberration – the focusing of different colors of light at different distances behind a lens
Corrected by using a series of converging and diverging lenses made up of different types of glass

10. Lens Aberrations