22_Ch 25 College Physics ProblemCH25 Optical Instruments

22_Ch 25 College Physics ProblemCH25 Optical Instruments -...

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358 CHAPTER 25 (b) If the object distance must be 26.0 cm p = to position the image at , the actual focal length is 75.0 cm q =− () ( ) 26.0 cm 75.0 m 26.0 cm 75.0 pq f pq == +− cm 0.398 cm = and 11 2.51 0.398 m f = + P ( diopters The error in the power is ) 2.67 2.51 diopter ∆= P s 0.16 diop = ters too low 25.50 (a) If q = when , the thin lens equation gives the focal length as 2.00 cm 1.00 m 100 cm p 100 c cm 100 cm pq f m 2.00 cm 1.96 2.00 cm = ++ (b) The f -number of a lens aperture is the focal length of the lens divided by the diameter of the aperture. Thus, the smallest f -number occurs with the largest diameter of the aperture. For the typical eyeball focused on objects 1.00 m away,
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