Lecture 19 Notes

# Lecture 19 Notes - Recap of last lecture Light can also be...

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Recap of last lecture Light can also be polarized by reflection. It is 100% polarized in the direction parallel to the reflecting surface when the angle of incidence = brewster angle = tan -1 (n b /n a ) Scattered light perpendicular to the direction of propagation of the primary beam is polarized. Two linearly polarized waves with their polarization directions perpendicular to each other and 90 0 out of phase with each other will superpose to give circularly polarized waves. Certain materials such as Calcite have two indices of refraction along different directions. Thus these type of materials can be used to introduce phase difference between two linearly polarized light beams. If the phase difference is λ /4 (90 0 ) (determined by the thickness of the material) the emerging light beam is circularly polarized. Such a plate would be called a quarter wave plate.

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Answers to reading quiz The color of the sky is often attributed to Raleigh scattering of sun light by air molecules. This scattering is stronger for shorter wavelengths of light (i.e. violet light scatters most and red light scatters the least). Q1. If violet light suffers stronger Raleigh scattering than blue light, why doesn't the sky appear violet? The sky appears blue because the violet and blue colors mix giving the sky the color we see. the sky isn't exactly blue, its a mixture of violet and blue. Because the intensity ratio for the blue is higher. Higher frequency wavelengths are emmited at lower intensities. Blue light has a lower frequency than violet, and will have a greater intesity(will be brighter). The violet light is dominant but still combines with other light which increases the average wavelength of the light we see in the sky, making it visible as a blue instead of violet.
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Lecture 19 Notes - Recap of last lecture Light can also be...

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