SMU Honors Physics. Announcements, Reminders and Spectroscopy! Instructors Eric Godat and Rick Guarino

Transcription

1 SMU Honors Physics Announcements, Reminders and Spectroscopy! Instructors Eric Godat and Rick Guarino

2 Announcements Teams (next slide) Next Week: NO CLASS!!! (Use this time to meet with your groups) Two Weeks: First Honors Collaboration Meeting Should have met with your team 2-3 times by then, and be ready to present your progress on the Grand Challenge Problem (see the last page of the syllabus) You will need a few slides to present your progress, prepare to talk for about 10 minutes (that includes questions from the audience) Eric Godat - SMU 2/13

3 Teams and s Team Alpha Meyer Willson (mwillson), Rachael LaCour (rlacour), Alexandra Randolph (arandolph) Team Beta Jose Saucedo (jsaucedo), Matt Witz (mwitz), Drew Stull (dstull) Eric Godat - SMU 3/13

4 Grand Challenge Reminder Eric Godat - SMU 4/13

5 Star Stuff and Light Light and its components Why are we Star Stuff? What color is the Sun? Atoms, Ionization, and Atomic Spectra What can we learn from Starlight? Eric Godat - SMU 5/13

6 You might be familiar with Isaac Newton's famous studies of white light, which when passed through a prism were seen to break into the rainbow of colors we are familiar with after a rain storm. The bottom (2) picture shows Newton's kind of experiments. We will use a more modern instrument, a Diffraction Grating, (1) that consists of many closely spaced slits. The wave nature of light causes light that passes through the many slits to interfere with itself, and different colors (wavelengths) of light will scatter at different angles. You will see the spectrum of a given material off to one side or the other of the light source as you look through the diffraction grating. Eric Godat - SMU 6/13

7 PRACTICE USING THE DIFFRACTION GRATINGS If you master the grating quickly, and if you have a camera phone with you, try taking a photo of the spectrum using your phone. I was able to do this with my Nexus 6, but your mileage may vary...! LAMP ATOMIC SPECTRUM Eric Godat - SMU 7/13

8 Star Stuff Elements are formed as a part of the stellar life cycle Light elements are formed due to fusion Heavy elements are formed in stellar death, such as Super Nova Eric Godat - SMU 8/13

9 Atoms and Light Ionization and Spectra are due to quantum mechanics Electrons in orbitals can absorb/emit only certain energy photons Different atoms have different spectra Essentially a light fingerprint You have several spectra on your printouts Several more here: Eric Godat - SMU 9/13

10 Your eye can only see light with a wavelength between about nm, corresponding to narrow range of atomic transitions. Eric Godat - SMU 10/13

11 Starlight: Cosmic Information Assumption: matter out in the cosmos is made from the same atoms as the ones we find or make on Earth Assess: look at light from distant objects (e.g. the sun). Compare spectral lines to known lines from atoms on Earth. What is the composition of the sun? Apply: look at light from more distant object stars, galaxies, supernova explosions, etc. - what atoms are present in these? The spectral lines are like atomic DNA we can determine the composition of distant alien places without visiting them in person. Eric Godat - SMU 11/13

12 Starlight: Exoplanets Doppler Shifting due to gravitational interactions Regular shifting tells us about orbital mechanics Proxima b Absorption from exoplanet atmosphere Presence of certain elements could hint at life Article about starlight: Eric Godat - SMU 12/13

13 Sodium Atomic and Quantum Physics The bright, dominant sodium doublet spectral lines from ionizing sodium atoms. This is shot using a camera, a spectrograph, and an electrified pickle! Spin-Orbit Splitting SOURCE: Eric Godat - SMU 13/13