week04 - Today Please turn in lab report 1 (on elms or give...

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Today Today’s class • the eye and simple optical instruments (magnifier, microscope, telescope) • start lab 2, lenses • Please turn in lab report 1 (on elms or give me paper) • for next week, HW3
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The Eye Eye can be modeled as a positive lens system. Bending of light rays occurs at: • the air-cornea interface (73% of bending) • aqueus-lens interface and lens-vitreous interface: fine-tuning of focusing. Shape controlled by ciliary muscle. Muscle is relaxed for distance viewing, tensed for near field viewing . (if the muscle did not tense, where would the image of a near object be? In front or behind the nerves?) Image is focused on retina, where light energy is converted to electrochemical energy Diameter: 22mm When the ciliary muscle is relaxed, distant objects are in focus. When it tenses, a young person can see an object that is only 7-10 cm away (“near point”). For a middle aged person, this increases to 25 cm away. (hold a book up and bring towards your face)
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magnifiers α NP tan = h 25 cm if you put the object at f 1 s + 1 s ' = 1 f s ' = M = h f M = M NP = 25 cm f 2X magnifier means the angle subtended is twice as large. This magnifier would have a focal length of 12.5 cm.
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Two lenses 1 s o + 1 s i 1 = 1 f 1 s i 1 = s o f 1 s o f 1 S i1 is object for second lens. Object distance is L-S i1 (negative number) 1 s i 2 1 s o 2 = 1 f 2 s i 2 = f 2 s o 2 s o 2 f 2 = f 2 ( L s i 1 ) L s i 1 f 2
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This note was uploaded on 12/29/2011 for the course PHYSICS 375 taught by Professor Eno during the Spring '11 term at Maryland.

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week04 - Today Please turn in lab report 1 (on elms or give...

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