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Class 9 Science Chapter 18 Observing Space:, , Telescopes Textbook Questions and Answers, , 1. Fill in the blanks with the proper words., , a. The wavelength of visible light is between, wee IN wee cecseeseeteseeeeeeee +, , b. GMRT is used fOF ..........eceeeeeeeee WAVES., , c. Acertain X-ray telescope is named after, , SCIENTIST ote, , d. The first scientist to use a telescope for, , space observations... «, , e. The biggest optical telescope in India is, , Situated at woes
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ANSWER:, , a. The wavelength of visible light is between, 400 nm and 800 nm., , b. GMRT is used for radio waves., , c. Acertain X-ray telescope is named after, scientist Subramanian chandrashekhar., , d. The first scientist to use a telescope for, space observation was Galileo Galilei., , e. The biggest optical telescope in India is, situated at Aryabhatt Research Institute of, Experimental Sciences, Nanital.
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2. Form pairs, , Column ‘A’, (1) X-rays, (2) Optical telescope, , (3) Indian radio, , telescope, , (4) Launching, , artificial-satellite, , Answer:, (1 - d),, (2 -c),, (3 - a),, (4 - b),, , Column ‘B’, (a) GMRT, (b) ISRO, , (c) Hubble, , (d) Chandra
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Question 3:, , What are the difficulties in using ground based, optical telescopes? How are they overcome?, , ANSWER:, , The difficulties faced in using ground based, telescopes due to which it does not make good, quality observations are:, , e Intensity of light rays reaching the Earth's, surface decreases as some of the light is, absorbed by the atmosphere., , ¢ The change in atmospheric pressure and, temperature cause the light rays to, change their path slightly and thus shake, the position of the image., , ¢ We cannot use optical telescopes during, day time because of the presence of, sunlight., , e Even in night, city lights and cloudy, weather can cause hindrance in observing, the heavenly bodies., , To overcome the above problems, telescopes, are now being erected in space itself. Some of, the telescopes in space are:, , ¢ Hubble telescope: It is an optical, telescope launched by the National, Aeronautics and Space Administration in, 1990. It is orbiting the Earth at a height of, 589 km from it and has a mirror, of diameter 94 inches., , ¢ Chandra: It is an X-ray telescope launched, by the National Aeronautics and Space, Administration in 1999. Special mirrors, which can reflect X-rays are used in this, telescope.
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4. Which type of telescopes can be made using, a concave mirror, convex mirror, plane mirror,, and a lens? Draw diagrams of these telescopes., , Answer:, , + A Newtonian telescope can be made, , using a concave mirror, plane mirror and a, , lens., , > Eyepiece, Concave mirror, , Light source, Plane mirror, Light source, MaharashtraBoardSolutions.com, The Newtonion telescope, , « A Cassegrain telescope can be made, , using a convex mirror, concave mirror and, , a lens., Light source, , , , Light source, MaharashtraBoardSolutions.com Concave mirror, The Cassegrain telescope, , * A refracting telescope can be made using, , two or more lenses., , A, A, te Eyepiece, Source Objective, of light lens
