Chapter 06

Chapter 06 - Note that the following lectures include...

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Note that the following lectures include animations and PowerPoint effects such as fly ins and transitions that require you to be in PowerPoint's Slide Show mode (presentation mode).
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Light and Telescopes Chapter 6
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Previous chapters have described the sky as it appears to our unaided eyes, but modern astronomers turn powerful telescopes on the sky. Chapter 6 introduces us to the modern astronomical telescope and its delicate instruments. The study of the universe is so challenging, astronomers cannot ignore any source of information; that is why they use the entire spectrum, from gamma rays to radio waves. This chapter shows how critical it is for astronomers to understand the nature of light. In each of the chapters that follow, we will study the universe using information gathered by the telescopes and instruments described in this chapter. Guidepost
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I. Radiation: Information from Space A. Light as a Wave and a Particle B. The Electromagnetic Spectrum II. Optical Telescopes A. Two Kinds of Telescopes B. The Powers of a Telescope C. Buying a Telescope D. New-Generation Telescopes E. Interferometry III. Special Instruments A. Imaging Systems B. The Spectrograph Outline
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IV. Radio Telescopes A. Operation of a Radio Telescope B. Limitations of the Radio Telescope C. Advantages of Radio Telescopes V. Space Astronomy A. Infrared Astronomy B. Ultraviolet Astronomy C. X-Ray Astronomy D. Gamma-Ray Telescopes E. Cosmic Rays F. The Hubble Space Telescope Outline (continued)
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Light and Other Forms of Radiation The Electromagnetic Spectrum In astronomy, we cannot perform experiments with our objects (stars, galaxies, …). The only way to investigate them, is by analyzing the light (and other radiation) which we observe from them.
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Light as a Wave (1) Light waves are characterized by a wavelength λ and a frequency f. f = c/ λ c = 300,000 km/s = 3*10 8 m/s f and λ are related through λ
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Light as a Wave (2) Wavelengths of light are measured in units of nanometers (nm) or Ångström (Å): 1 nm = 10 -9 m 1 Å = 10 -10 m = 0.1 nm Visible light has wavelengths between 4000 Å and 7000 Å (= 400 – 700 nm) .
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Wavelengths and Colors D i f f e r e n t colors of visible light correspond to different wavelengths.
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Light as Particles Light can also appear as particles, called photons (explains, e.g., photoelectric effect). A photon has a specific energy E, proportional to the frequency f: E = h*f h = 6.626x10 -34 J*s is the Planck constant . The energy of a photon does not depend on the intensity of the light!!!
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The Electromagnetic Spectrum Need satellites to observe Wavelength Frequency High flying air planes or satellites
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Astronomers use telescopes to gather more light from astronomical objects. The larger the
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This note was uploaded on 11/04/2011 for the course PHYS 227 taught by Professor Professorroberts during the Fall '11 term at BYU.

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Chapter 06 - Note that the following lectures include...

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