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Refraction PowerPoint Presentation

Refraction

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Refraction

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Presentation Transcript

  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