Refraction Optical Phenomena

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)

Total Internal Reflection

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

Atmospheric Refraction

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

Dispersion

Dispersion

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

Lens Aberrations