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Spectroscopy

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A short investigatory project on Spectroscopy.
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  1   Project Submitted by: Sumit Anand Class: XII-A    AFS OJHAR CHEMISTRY INVESTIGATORY PROJECT WORK  2   CONTENTS   S.No. Title 1 Introduction 2 Physical Quantities measured 3 What Is Spectroscopy 4 Nature of light 5 The Electromagnetic Spectrum 6 General Types of Spectra 10 Types of Spectroscopy 11 How Spectrometer work? 12 Types of Spectroscopy 13 Examples of Spectroscopy in Astronomy 14 Probing the Formation of Stars in Colliding Galaxies in the universe. 15 Uncovering the mystery of quasar   16 Spectroscopy in Astronomy camp 17 Stars like our own Sun 18 Bibliography  3      Kinetic energy of particles is studied by electron energy loss spectroscopy and  Auger electron spectroscopy (see also cross section).     The mass-to-charge ratios of molecules and atoms are studied in mass spectrometry, sometimes called mass spectroscopy . Mass spectrometry is more of a measuring technique (metric) than an observation (scope) technique but can Produce a spectrum of masses, a mass spectrum, similar in appearance to other spectroscopy techniques.     The number of molecules or atoms or quantum-mechanical states to which the frequency or energy parameter applies. In this case the spectrum is usually called cross section. What is Spectroscopy?   Spectroscopy pertains to the dispersion of an object's light into its component colors (i.e. energies). By performing this dissection and analysis of an object's light, astronomers can infer the physical properties of that object (such as temperature, mass, luminosity and composition). But before we hurtle headlong into the wild and woolly field of spectroscopy, we need to try to answer some seemingly simple questions, such as what is light ? And how does it behave ? These questions may seem simple to you, but they have presented some of the most difficult conceptual challenges in the long history of physics. It has only been in this century, with the creation of quantum mechanics that we have gained a quantitative understanding of how light and atoms work. You see, the questions we pose are not always easy, but to understand and solve them will unlock a new way of looking at our Universe. The Nature of Light   To understand the processes in astronomy that generate light, we must realize first that light acts like a wave . Light has particle-like properties too, so it's actually quite a twisted beast (which is why it took so many years to figure out). But right now, let's just explore light as a wave. Picture yourself wading around on an ocean beach for a moment, and watch the many water waves sweeping past you. Waves are disturbances, ripples on the water, and they possess a certain height ( amplitude ), with a certain number of waves rushing past you every minute (the  frequency ) and all moving at a characteristic speed across the water (the wave speed ). Notice the distance between successive waves? That's called the wavelength .  4   Notice that radio, TV, and microwave signals are all light waves, they simply lie at wavelengths (energies) that your eye doesn't respond to. On the other end of the scale, beware the high energy UV, x-ray, and gamma-ray photons! Each one carries a lot of energy compared to their visible- and radio-wave brethren. They're the reasons you should wear sunblock, for example. When we look at the Universe in a different light , i.e. at non-visible wavelengths, we probe different kinds of physical conditions -- and we can see new kinds of objects! For example, high-energy gamma-ray and X-ray telescopes tend to see the most energetic dynamos in the cosmos, such as active galaxies, the remnants from massive dying stars, accretion of matter around black holes, and so forth. Visible light telescopes best probe light produced by stars. Longer- wavelength telescopes best probe dark, cool, obscured structures in the Universe: dusty star-forming regions, dark cold molecular clouds, the primordial radiation emitted by the formation of the Universe shortly after the Big Bang. Only through studying astronomical objects at many different wavelengths are astronomers able to piece together a coherent, comprehensive picture of how the Universe works!   General Types of Spectra   Typically one can observe two distinctive classes of spectra: continuous and discrete. For a continuous spectrum, the light is composed of a wide, continuous range of colors (energies). With discrete spectra, one sees only bright or dark lines at very distinct and sharply-defined colors (energies). As we'll discover shortly, discrete spectra with bright lines are called emission spectra, those with dark lines are termed absorption spectra.    Continuous Spectra   Continuous spectra arise from dense gases or solid objects which radiate their heat away through the production of light. Such objects emit light over a broad range of wavelengths, thus the apparent spectrum seems smooth and continuous. Stars emit light in a  predominantly (but not completely!) continuous spectrum. Other examples of such objects are incandescent light bulbs, electric cooking stove burners, flames, cooling fire embers and... You. Yes, you, right this minute, are emitting a continuous spectrum -- but the light waves you’re emitting are not visible -- they lie at infrared wavelengths (i.e. lower energies, and longer wavelengths than even red light). If you had infrared-sensitive eyes, you could see people by the continuous radiation they emit !
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