Optical Instruments361From the thin lens equation, the image distance of the objective lens in this case is ()( )111300 cm20.0 cm21.4 cm300 cm20.0 cmpfq===−−2.00 cmefWith an eyepiece of focal length =, the angular magnification for this telescope is 121.4 cm10.72.00 cmeqmf=25.56We use 122nnnn1pqR−+=, with p→ ∞and qequal to the cornea to retina distance. Then, 2121.32.00 cm0.507 cm5.07 mmnnRqn==41.001.3425.57 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 cmfq==. (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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