1 / 25

Unit 4

Unit 4. Atomic Physics and Spectra. The Electromagnetic Spectrum. Waves. type of disturbance that can propagate or travel. wavelle  lnlgth (  )‏. crest. Equilibrium position. amplitude (A)‏. trough. velocity (v)‏.

hester
Download Presentation

Unit 4

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit 4 Atomic Physics and Spectra

  2. The Electromagnetic Spectrum

  3. Waves • type of disturbance that can propagate or travel. wavelle  lnlgth()‏ crest Equilibrium position amplitude (A)‏ trough velocity (v)‏ Wavelength ()is a distance, so its units are m, cm, or mm, etc. Period (T): time between crest (or trough) passages Frequency(n): rate of passage of crests (or troughs c= n (units: Hertz or cycles/sec)‏

  4. Shorter wavelength (l) = higher frequency (n) and therefore higher energy

  5. Refraction Waves bend when they pass through material of different densities. air water swimming pool prism glass air air

  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

  7. Electromagnetic Radiation How we get information about the cosmos e.g. Visible Light‏

  8. The Electromagnetic Spectrum 1 nm = 10 -9 m , 1 Angstrom = 10 -10 m n c =

  9. Refraction of light When you bend light, bending angle depends on wavelength, or color. (Prism demo)‏

  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. "Absorption” Spectrum cool, thin gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place, superimposed on the continuous spectrum.

  11. Pattern of lines is a fingerprint of the element

  12. For a given element, emission and absorption lines occur at the same wavelengths. Sodium emission and absorption spectra

  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. 

  14. The Nature of Atoms The Bohr model of the Hydrogen atom: electron _ _ + + proton "ground state" "excited state"

  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

  16. Other elements Helium Carbon neutron proton Each element has its own allowed energy levels yielding a unique spectral fingerprint.

  17. Atmospheric blocking

  18. Radio Waves • Emitted by TV, radio, stars, galaxies • Radio wave image of CO gases in our Milky Way galaxy

  19. Microwaves • Penetrate clouds, fog  communication, radar

  20. Infrared • Thermal (heat) IR image of Milky Way

  21. Visible • Detection with eyes

  22. Ultraviolet • Higher energy than visible light UV image of the Sun

  23. X ray radiation X ray image of the Sun

  24. Gamma-rays • Shortest wavelength, therefore highest E • Produced by supernovae, pulsars, black holes, … • Gamma ray bursts  (source ???)

  25. http://science.hq.nasa.gov/kids/imagers/ems/gamma.html • https://www.e-education.psu.edu/astro801/content/l3_p4.html

More Related