unit 4 atomic physics and spectra. the electromagnetic spectrum

Download Unit 4 Atomic Physics and Spectra. The Electromagnetic Spectrum

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  • Slide 1
  • Unit 4 Atomic Physics and Spectra
  • Slide 2
  • The Electromagnetic Spectrum
  • Slide 3
  • Waves type of disturbance that can propagate or travel. wavelle lnlgth ( ) crest amplitude (A) velocity (v) trough Wavelength ( is a distance, so its units are m, cm, or mm, etc. Period (T): time between crest (or trough) passages Frequency ( ): rate of passage of crests (or troughs c= (units: Hertz or cycles/sec) Equilibrium position
  • Slide 4
  • Shorter wavelength ( ) = higher frequency ( ) and therefore higher energy
  • Slide 5
  • Waves bend when they pass through material of different densities. swimming pool air water prism air glass Refraction
  • Slide 6
  • All radiation (including visible light) travels as Electromagnetic waves. Examples of objects with magnetic fields: Magnet the Earth the Sun Examples of objects with electric fields: Electrical appliances Lightning Protons, electrons
  • Slide 7
  • Electromagnetic Radiation How we get information about the cosmos e.g. Visible Light
  • Slide 8
  • c = 1 nm = 10 -9 m, 1 Angstrom = 10 -10 m The Electromagnetic Spectrum
  • Slide 9
  • When you bend light, bending angle depends on wavelength, or color. Refraction of light (Prism demo)
  • Slide 10
  • Types of Spectra 1. "Continuous" spectrum luminous solid, liquid, or dense gas, emits light of all wavelengths, produces a continuous spectrum 2. "Emission" spectrum low-density, hot gas emits light whose spectrum consists of a series of bright emission lines that are characteristic of the composition of the gas. 1."Absorption Spectrum c ool, thin gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place, superimposed on the continuous spectrum.
  • Slide 11
  • Pattern of lines is a fingerprint of the element
  • Slide 12
  • For a given element, emission and absorption lines occur at the same wavelengths. Sodium emission and absorption spectra
  • Slide 13
  • The Particle Nature of Light Light interacts with matter as individual packets of energy, called photons. photon energy is proportional to frequency: example: ultraviolet photons are more dangerous than visible photons.
  • Slide 14
  • The Nature of Atoms The Bohr model of the Hydrogen atom: _ + proton electron "ground state" _ + "excited state"
  • Slide 15
  • When an atom absorbs a photon, it moves to a higher energy state briefly When it jumps back to lower energy state, it emits photon(s) in a random direction, conserving the total energy of the system
  • Slide 16
  • Other elements Helium Carbon neutron proton Each element has its own allowed energy levels yielding a unique spectral fingerprint.
  • Slide 17
  • Atmospheric blocking
  • Slide 18
  • Radio Waves Emitted by TV, radio, stars, galaxies Radio wave image of CO gases in our Milky Way galaxy
  • Slide 19
  • Microwaves Penetrate clouds, fog communication, radar
  • Slide 20
  • Infrared Thermal (heat) IR image of Milky Way
  • Slide 21
  • Visible Detection with eyes
  • Slide 22
  • Ultraviolet Higher energy than visible light UV image of the Sun
  • Slide 23
  • X ray radiation X ray image of the Sun
  • Slide 24
  • Gamma-rays Shortest wavelength, therefore highest E Produced by supernovae, pulsars, black holes, Gamma ray bursts (source ???)
  • Slide 25
  • http://science.hq.nasa.gov/kids/imagers/ems/ gamma.html http://science.hq.nasa.gov/kids/imagers/ems/ gamma.html https://www.e- education.psu.edu/astro801/content/l3_p4.ht ml https://www.e- education.psu.edu/astro801/content/l3_p4.ht ml

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