25_Chapter 25 HomeworkCH25 Optical Instruments

25_Chapter 25 HomeworkCH25 Optical Instruments - Optical...

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Optical Instruments 361 From the thin lens equation, the image distance of the objective lens in this case is () ( ) 11 1 300 cm 20.0 cm 21.4 cm 300 cm 20.0 cm pf q == = −− 2.00 cm e f With an eyepiece of focal length = , the angular magnification for this telescope is 1 21.4 cm 10.7 2.00 cm e q m f = 25.56 We use 122 nnnn 1 p qR += , with p → ∞ and q equal to the cornea to retina distance. Then, 21 2 1.3 2.00 cm 0.507 cm 5.07 mm nn Rq n  = =   4 1.00 1.34 25.57 When a converging lens forms a real image of a very distant object, the image distance equals the focal length of the lens. Thus, if the scout started a fire by focusing sunlight on kindling 5.00 cm from the lens, 5.00 cm fq = = . (a) When the lens is used as a simple magnifier, maximum magnification is produced when the upright, virtual image is formed at the near point of the eye (
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