HW12-solutions

# HW12-solutions - gilbert (amg3448) HW12 tsoi (57210) This...

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gilbert (amg3448) – HW12 – tsoi – (57210) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points The bellows oF an adjustable camera can be extended so that the largest distance From the lens to the flm is 1 . 52 times the Focal length. IF the Focal length oF the lens is 6 . 75 cm, what is the distance From the closest object that can be sharply Focused on the flm? Correct answer: 19 . 7308 cm. Explanation: The mirrors and lenses have the property: 1 p + 1 q = 1 f Here q = k × f So p = kf k - 1 = (1 . 52)(6 . 75 cm) 1 . 52 - 1 =19 . 7308 cm 002 10.0 points AF a r - s i g h t e ds t u d e n th a san e a rp o i n to F 163 cm. Calculate the Focal length oF the glasses needed so the near point will be normal (25 cm). Neglect the space between the eyes and the eye-glasses. Correct answer: 29 . 529 cm. Explanation: Basic Concepts 1 p + 1 q = 1 f Solution: We want to insert a lens such that, when an object is placed at the normal near point oF 25 cm, an image is Formed at -163 cm. This image then becomes the object For the lens in the student’s eye. Using the thin lens equation we have f = ± 1 p + 1 q ² - 1 = ± 1 25 cm + 1 - 163 cm ² - 1 =29 . 529 cm . Alternative solution: Without glasses, 1 163 cm + 1 q = 1 f , where q and f are For the near point case. With glasses, 1 25 cm + 1 q = 1 f + 1 f glasses . So 1 f glasses = 1 25 cm - 1 163 cm f glasses . 529 cm 003 (part 1 of 3) 10.0 points Apersonwithanearsightedeyehasnearand Far points oF 15 cm and 26 cm, respectively. Assuming a lens is placed 1 . 3cmFromthe eye, what power must the lens have to correct this condition? Correct answer: - 4 . 04858 diopter. Explanation: Given : d near =15cm , d far =26cm , Δ d =1 . 3cm , and q 1 = - ( d far - Δ d )= - 24 . 7cm . To correct the eye, a distant object should Form a virtual image at the Far point through the lens.

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## This note was uploaded on 03/29/2012 for the course PHY 302l taught by Professor Morrison during the Spring '08 term at University of Texas.

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HW12-solutions - gilbert (amg3448) HW12 tsoi (57210) This...

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