10_Chapter 25 HomeworkCH25 Optical Instruments

10_Chapter 25 HomeworkCH25 Optical Instruments - 346...

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346 CHAPTER 25 (b) The lower part of the lens should form an upright, virtual image at the near point of the eye ( ) 30 cm q =− when the object distance is 25 cm p = . From the thin lens equation, () ( ) 2 30 cm 1.5 10 cm 30 cm f = + × +− 25 cm 25 cm pq pq == 1.5 m = + Therefore, the power is 11 0.67 1.5 m f = + + P diopters 25.17 (a) The simple magnifier (a converging lens) is to form an upright, virtual image located 25 cm in front of the lens ( ) 25 cm q . The thin lens equation then gives ( )( ) 25 cm 7.5 cm 25 cm 7.5 cm qf p qf −− − 5.8 cm = + so the stamp should be placed 5.8 cm in front of the lens
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