Monday 3pm practice math and prepare for test. Phys 1830: Lecture 8 Tutorial/Office hour Monday 3pm practice math and prepare for test. 1 tutorial away! Use your iClicker even if you haven’t registered it with me yet! Do NOT register it online for this class. Change of password iclicker report on wall. check the number on the clicker. attach it to your name. if your student number isn’t on the roster then email me with your name, iclicker number, and student number AND COURSE. Quizzes are from the previous Friday and the current Monday and Wednesday. No planetarium tonight. Contact Mr. Cameron.

Organization of Physics Undergraduate Students. OPUS! Help with math. Organization of Physics Undergraduate Students. Tutoring Schedule: Posted on the door of the tutoring lab. Where the tunnel from Armes meets the tunnel going to University Centre. Face the bank machine, look left  Allen Building. Go into Allen and go right to the tutoring office. Or go down left hand corridor to find their office and directions to the tutoring office. Or follow me after class 

University of Manitoba Astronomy Club Special Club! Contact: umastroclub@gmail.com Wonder about the origins of the Universe? Curious about black holes? Come out and help design the club activities! No need to be a geek  Meeting Wednesday at 5:30 pm in Allen 330

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Phys 1830: Lecture 8 Test Friday Jan 30th 500° K 1000° K 2000° K 5000° K 10,000° K 20,000° K X-Ray Ultraviolet Visible Infrared Microwave Radio Intensity Test Friday Jan 30th In class. See online handout. Includes telescopes (Wednesday’s material) Upcoming Topics How the interaction of light and matter produce spectra. Optical Telescopes Radio Telescopes B&W imaging workshop – scheduled Monday Feb 2 Previous class: Light, electromagnetic radiation Wavelength, frequency Thermal radiation This class: thermal radiation continued Kirchhoff’s Laws Spectra

The Interaction of light and matter. summary Recall column Photons and matter interact creating spectra. spectra can be used to assess temperature (blackbody curve type spectrum) processes that produce light or absorb it (i.e. what is going on) (Demo) (Animation)

Kirchhoff’s Laws Spectra 3 empirical laws summary Recall column Kirchhoff’s Laws 3 empirical laws Hot opaque body -> continuous spectrum Cooler transparent gas between source & observer -> absorption line spectrum Diffuse, transparent gas -> emission line spectrum  means “gives” Astronomical objects have spectral “finger prints”. Also called “Continuum emission” can be produced by a hot dense gas. (Like a light bulb – a rainbow of colours.) If we plot this as intensity versus wavelength this produces a blackbody curve. c) Emission lines are produced by diffuse (low density) gas. (Like a neon sign.) b) Place the diffuse gas in front of the hot, gas and absorption-lines are created. There is the continuum (rainbow) with dark absorption lines where the emission lines would be. (see animation)

Spectra This kind of spectrum (continuum) is caused by summary Recall column This kind of spectrum (continuum) is caused by Hot, low density gas Hot, dense blackbody Cooler transparent gas

Continuum rainbow-like spectrum Dark line absorption spectrum Spectra Our sun and other stars have an atmosphere. Imagine that you are in a spaceship far above the Earth’s atmosphere. Which of the following spectra would you observe when analyzing sunlight? Continuum rainbow-like spectrum Dark line absorption spectrum Bright line emission spectrum Discuss with your neighbours.

Spectral Finger Prints Solar Spectrum Note that the emission lines for the lab spectrum of iron are at the same wavelengths of the absorption lines of iron in the sun. We can use line spectra to determine the chemical elements in an object.

Interaction of Light and Matter: How are line spectra created? Photons of light interact with atoms and molecules. Atoms consist of: Electrons (negative charge) Nuclei (balance charge of electrons) Protons (positive charge) Neutrons (neutral charge) Molecules are a group of 2 or more atoms. This happens to be a helium atom.

Interaction of Light and Matter Hydrogen is the simplest atom. 1 electron and 1 proton. Classical picture is that the electron is in an orbit. Contemporary picture represents the electron as a cloud. Orbits are really energy levels.

Interaction of Light and Matter Hydrogen Atom Energy Levels Every chemical element has its own specific set of energy levels. Each energy level is associated with a wavelength. Recall energy is E=h * frequency and c = wavelength * frequency. So substituting for frequency we can see that E is associated with wavelength.

Interaction of Light and Matter Creating spectral lines at visible wavelengths There are specific (quantized) energy levels. The level with the lowest energy is the ground state. How does the electron get excited into a state with higher energy? By interactions between photons and matter.

Interaction of Light and Matter: Creating spectral lines at visible wavelengths The electron can shift between energy levels by absorption and emission of photons.