# Ch6 - Assignment Chapter 6 Class Astronomy I Date September...

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Assignment: Chapter 6 Class: Astronomy I Date: September 12 th , 2007 Review Questions 1. Describe refraction and reflection. Explain how these processes enable astronomers to build telescopes. Refracting telescopes produce images by bending light rays as they pass through glass lenses, while reflecting telescopes produce images by reflecting light rays to a focus point from curved mirrors. 2. Explain why a flat piece of glass does not bring light to a focus while a curved piece of glass can. The refraction causes all the rays to converge at a point called the focus because the lens’ convex shape bends all the light to one point. A flat piece of glass will not bend the direction of the rays, therefore only letting the light go through parallel. 3. Explain why the light rays that enter a telescope from an astronomical object are essentially parallel. The stars are so far away that only a few of the light rays will enter the lens, and they will essentially be parallel. 4. With the aid of a diagram, describe a refracting telescope. Which dimensions of the telescope determine its light-gathering power? Which dimensions determine the magnification? Refracting telescope consists of a large-diameter objective lens that determines its light- gathering power, and the eyepiece lens that magnifies the image for easier viewing. 5. What is the purpose of the telescope eyepiece? What aspect of the eyepiece determines the magnification of the image? In what circumstances would the eyepiece not be used? The eyepiece lens magnifies the image for the observer. Its smaller, shorter focal-length lens at the rear of the telescope magnifies the image. But beyond a certain point of magnification, further use of the eyepiece can make the blurred image less clear. 6. Do most professional astronomers actually look through their telescopes? Why or why not? Yes, because it allows them to detect fainter objects more clearly. 7. Quite often advertisements appear for telescopes that extol their magnifying power. Is this a good criterion for evaluating telescopes? Explain your answer. Beyond a certain point, nothing more can be gained by further magnification. Astronomers put more store in the light-gathering power than in magnification. 8. What is chromatic aberration? For what kinds of telescopes does it occur? How can it be corrected? Chromatic aberration refers to the optical defect in refracting telescopes, in which different colors don’t focus at the same point and the lens is surrounded by fuzzy, rainbow-colored halos. This can be corrected by using an objective lens that is not just a single piece of glass but two different kinds of glass for the two lenses. Last Name: Sung First Name: Myung Hyun

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Assignment: Chapter 6 Class: Astronomy I Date: September 12 th , 2007 9. With the aid of a diagram, describe a reflecting telescope. Describe four different ways in which an astronomer can access the focal plane. Reflecting telescope consists of a curved mirror to make an image of a distant object.
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## This note was uploaded on 08/25/2008 for the course ASTRON 1 taught by Professor Jsepikas during the Winter '07 term at Pasadena City College.

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Ch6 - Assignment Chapter 6 Class Astronomy I Date September...

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