copyright © by holt, rinehart and winston. all rights reserved. chapter 1 section 2 telescopes...
TRANSCRIPT
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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 1 Section 2 Telescopes
• Compare refracting telescopes with reflecting telescopes.
• Explain how the atmosphere limits astronomical observations, and explain how astronomers overcome these limitations.
• List the types of electromagnetic radiation that astronomers use to study objects in space.
Objectives
Chapter 1
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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 1 Section 2 Telescopes
Telescopes
• A Telescope is an instrument that gathers electromagnetic radiation from objects in space and concentrates it for better observation.
• There are many different types of telescopes.
Chapter 1
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Chapter 1 Section 2 Telescopes
Optical Telescopes
• Refracting Telescopes Telescopes that use lenses to gather and focus light are called refracting telescopes. A refracting telescope is shown on the next slide.
• Reflecting Telescope A telescope that uses a curved mirror to gather and focus light is called a reflecting telescope. A reflecting telescope is shown on the next slide.
Chapter 1
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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 1 Section 2 Telescopes
Optical Telescopes
• Refracting Telescopes Telescopes that use lenses to gather and focus light are called refracting telescopes. A refracting telescope is shown on the next slide.
• Reflecting Telescope A telescope that uses a curved mirror to gather and focus light is called a reflecting telescope. A reflecting telescope is shown on the next slide.
Chapter 1
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Chapter 1 Section 2 Telescopes
Refracting and Reflecting Telescopes
Chapter 1
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Chapter 1 Section 2 Telescopes
Optical Telescopes, continued
• Very Large Reflecting Telescopes In some very large reflecting telescopes, several mirrors work together to collect light and focus it in the same area.
Chapter 1
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ResourcesChapter menu
• Most optical telescopes used by professional astronomers are housed in buildings called observatories.
Using Optical Telescopes
• Observatories often have dome-shaped roofs that can be opened up for viewing.
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ResourcesChapter menu
• The twin Keck reflecting telescopes have segmented mirrors 10 m wide.
Large Reflecting Telescopes
• Until 2000, these mirrors were the largest reflectors ever used.
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ResourcesChapter menu
Large Reflecting Telescopes
• In 2000, the European Southern Observatory’s telescope, in Chile, consisted
of four 8.2-m reflectors, making it the largest optical telescope in use.
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Chapter 1 Section 2 Telescopes
Optical Telescopes, continued
• Optical Telescopes and the Atmosphere The light gathered by telescopes on the Earth is affected by the atmosphere.
• Optical Telescopes in Space To avoid interference by the atmosphere, scientists have put telescopes in space
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ResourcesChapter menu
• The Hubble Space Telescope was launched in 1990 by the space shuttle Discovery.
Hubble Space Telescope
• In December 1993, a team of astronauts repaired the Hubble Space Telescope by installing a set of small mirrors designed to correct images obtained by the faulty mirror.
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ResourcesChapter menu
• Two more missions to service Hubble were carried out in 1997 and 1999.
Hubble Space Telescope
• Among the objects viewed by Hubble after it was repaired in 1999 was a large cluster of galaxies known as Abell 2218.
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Chapter 1 Section 2 Telescopes
Nonoptical Telescopes
• Radio Telescopes Radio telescopes detect radio waves. Because radio wavelengths are much larger than optical wavelengths, radio telescopes much be very large.
• Linking Radio Telescopes Astronomers can get more detailed images of the universe by linking radio telescopes together. Working together, the telescopes function as a single giant telescope.
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ResourcesChapter menu
Radio Telescopes
• Unlike visible light, radio waves pass freely through Earth’s atmosphere.
• Because of this, radio telescopes are useful 24 hours per day under most weather conditions.
• Radio waves reaching Earth’s surface strike the large, concave dish
of a radio telescope.
• This dish reflects the
waves to a focal point
where a receiver is located.
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Chapter 1 Section 2 Telescopes
Nonoptical Telescopes, continued
• Nonoptical Telescopes in Space Because most electromagnetic waves are blocked by the Earth’s atmosphere, scientists have placed ultraviolet telescopes, infrared telescopes, gamma-ray telescopes, and X-ray telescopes in space.
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Chapter 1
Electromagnetic Radiation• The electromagnetic spectrum includes the
entire range of radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.
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Chapter 1
Four Views of the Crab Nebula• Different type of telescopes collect
electromagnetic radiation at different wavelengths. Astronomers are able to learn a great deal about the Crab Nebula by examining these different images. The images are shown at different scales.
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Chapter 1 Section 2 Telescopes
The Electromagnetic Spectrum
• What Is the Electromagnetic Spectrum? The electromagnetic spectrum is made up of all of the wavelengths of electromagnetic radiation.
• Detecting Electromagnetic Radiation Visible light is only a small band of the electromagnetic spectrum. Radio waves, microwaves, infrared light, ultraviolet light, X rays, and gamma rays— are invisible to the human eye.
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Chapter 1 Section 2 Telescopes
The Electromagnetic Spectrum
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Chapter 1
“Gamma Rays”1x10-12 m
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Chapter 1
Individual Atoms! (Xe on Ni)5x10-11 m
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Chapter 1
“X-Rays”1x10-10 m
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Chapter 1
Width of DNA Helix2x10-9 m
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Chapter 1
“Average Virus”7.5x10-8 m
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Chapter 1
“Ultraviolet”5x10-8 m
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Chapter 1
“Average Bacterium”0.2 – 2.0x10-6 m
StaphylococcusCredit: E. Coli; Rocky Mountain Laboratories, NIAID, NIH
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Chapter 1
“Visible” light5x10-7 m
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Chapter 1
“Infared”1x10-5 m
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Chapter 1
“High Microwave”1x10-2 m
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Chapter 1
Height of “Average” Human1.7x100 m
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Chapter 1
“Radio/Low Microwave”1x10-2 – 1x103 m