Lecture 26

# Lecture 26 - Replacing the mirror was unthinkable. The...

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Recap of last lecture . When light has a wavelength l much smaller than objects that it interacts with, we can treat light as composed of straight-line rays. This regime is called geometric optics.

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Reflections from a spherical mirrors Mnemonic: Looking at a concave mirror is like looking into a “cave”, the light has to enter a surrounding region. A convex mirror is then the “other” kind of mirror. a + b = 2 f tan a = h/(s- d) tan b = h/(s’ - d) tan f = h/(R- d) Paraxial approximation when a is small we can neglect d and we get 1/s +1/s’ = 2/R = 1/f
The focal point and focal length of a spherical mirror

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The Hubble Space Telescope The HST has a spherical mirror. Unfortunately, it was ground to the wrong dimensions by 1/50 the width of a human hair over a mirror as large as a person.

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Unformatted text preview: Replacing the mirror was unthinkable. The final solution was an electronic adjustment to the photodiode array which converts the optical image to digital data. figure shows the dramatic before and after images. A concave mirror with a radius of curvature of 20 cm has a focal length of A. 40 cm B. 20 cm C. 10 cm D. 5 cm E. Answer depends on the refractive index of the medium surrounding the mirror Because F = R/2 A system of rays may be constructed to reveal the image The convex spherical mirror Which of the following changes its focal length when it is immersed in water? A. A concave mirror B. A convex mirror C. Both of these D. None of these Because reflection does not have anything to do with the refractive index of the medium....
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## This note was uploaded on 01/27/2012 for the course PH 2233 taught by Professor Dipinkardutta during the Spring '11 term at Mississippi State.

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Lecture 26 - Replacing the mirror was unthinkable. The...

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