Optical Instruments34325.7Since the exposure time is unchanged, the intensity of the light reaching the film should be doubled so the energy delivered will be doubled. Using the result of Problem 6 (part a), we obtain ()22212121-number-number11612IffI===, or 2-number617.8fThus, you should use the 8.0fsetting on the camera. 25.8To focus on a very distant object, the original distance from the lens to the film was . To focus on an object 2.00 m away, the thin lens equation gives 165.0 mmqf( )( )332.0010 mm65.0 mm67.2 mm2.0065.0 mm×=−×−222pfqThus, the lens should be moved qq∆= −2.2 mm farther from the filmq=25.9This patient needs a lens that will form an upright, virtual image at her near point (60.0
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