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Understand how light behaves when it hits transparent materials, reflecting and refracting based on the material's index of refraction. Dive into Snell's Law, lens types, focal length calculations, and lens aberrations. Discover why objects underwater appear closer to the surface. Explore vision issues and optical instruments like microscopes and telescopes.
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Some of it reflects and/or refracts • Refraction is the bending of light due to a change in it’s speed in the new material
Index of refraction • n = c/v 1 or greater
While θi=θr for reflection it isn’t always true for refraction, it depends in n • Snell’s Law • n1sinθ1 = n2sinθ2
So why do objects under the water look closer to the surface and farther away from us than they really are?
Lenses use refraction to redirect light • Converging – brings the light towards the axis • Diverging – directs the light away from the axis
Ray Diagrams • Converging • 1 – from tip parallel then towards f • 2 – from tip thru f then parallel • 3 – from tip thru center
Ray Diagram • Diverging • 1- parallel then away from f • 2- towards far f then parallel • 3 – thru center
Thin lens equation • Magnification equation
Signs • f + converging • do + on the left of lens • di + on the right of lens • m + for upright
Sketch a ray diagram for a converging lens with focal length of 1 m and the object 0.5 m left of the lens and 0.2 m tall. Then calculate the distance of the image as well as it’s height.
Eye Type of lense? • Near point – closest object distance that still gives a clear image • Far point – farthest object distance that still gives a clear image
Nearsightedness – far point issue, image in front of retina, use a diverging lens • Farsightedness – near point issue, image is behind the retina, use a converging lens
Microscope • Telescope
If n1 > n2 then there is an angle where θ2 = 90o • Sinθc = n2 / n1 • θc is the critical angle • If θ= θc then the “light” totally internally reflects
Since each wavelength refracts differently prisms cause the rainbow from white light • Also rainbows in the sky are caused by water droplets dispersing the light back towards us.
Lens Aberrations – not a single focal pt • Spherical aberrations – farther from the principal axis moves the focus • Chromatic aberrations – different wavelengths refracting differently