Solar Spectrum

1. Solar Spectrum

2. Bit of Administration …. • c = 3 x 108 m/sec = 3 x 105 km/sec • Reading • BSNV pp. 153 - 168

3. The Physics of Light • Doppler Shift

4. The Physics of Light • Doppler Shift • Source moving toward observer or • observer moving toward source Shorter Wavelength Higher Frequency Blueshift • Source moving away from observer or • observer moving away from source Longer Wavelength Lower Frequency Redshift

5. The Physics of Light • Doppler Shift • Source across (perpendicular to) observer’s line of sight Same Wavelength as emitted Same Frequency as emitted No Shift Doppler Shift only provides measure of radial velocity, or speed along the line of sight

6. The Physics of Light • Doppler Shift vrad = radial velocity of light source or observer (+ => away from each other) Dl = change (shift) in wavelength = lobserved - lrest lrest = rest wavelength c = 3 x 105 km/sec

8. ConcepTest! When Mars is in the middle of its retrograde loop, you expect it to show A large redshift No Doppler shift A large blue shift Depends on where it is in its orbit

9. The Physics of Light • Light as a Particle = Photons • Photon - A Discrete Unit of Light Energy • Planck’s Law h = Planck’s Constant = 6.626 x 10-34 joule sec l = wavelength in m, c = 3 x108 m/sec

10. The Physics of Light • Light as a Particle = Photons • Planck’s Law Small wavelength Large frequency Large energy Large wavelength Small frequency Small energy

11. The Physics of Light • Spectroscopy and Atomic Physics • Types of Spectra • Continuous - No spectral lines • Absorption - Dark lines superimposed on continuous spectrum • Emission - Isolated bright lines

12. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws • An opaque object emits a continuous spectrum. • An opaque object viewed through a cooler gas will produce an absorption spectrum. • A gas viewed against an empty background produces an emission spectrum

13. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws

14. The Physics of Light • Spectroscopy • Temperature - a measure of the speeds of particles Room Temperature 300 oK

15. The Physics of Light • Spectroscopy • Thermal Radiation - Any opaque object that has a • temperature above 0 oK emits light

16. The Physics of Light • Spectroscopy • Thermal Radiation

17. The Physics of Light • Spectroscopy • Thermal Radiation

18. The Physics of Light • Spectroscopy • Thermal Radiation • Wien Law lmax lmax in nm T in oK

19. Spectroscopy • Thermal Radiation • Wien Law • Stefan-Boltzmann Law The Physics of Light Eflux = energy emitted from square meter in one second • = Stefan-Boltzmann constant

20. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws

21. The Physics of Light • Spectroscopy and Atomic Physics • Quantum Mechanics - Electron can only be in certain specific • orbits <=> can only have certain specific energies Quantum Numbers e Hydrogen Atom

22. The Physics of Light • Spectroscopy and Atomic Physics • Quantum Mechanics - Electron energy changes can only have • certain values corresponding to energy changes between orbits • ==> only certain energies of photons can be absorbed or emitted

23. The Physics of Light • Spectroscopy and Atomic Physics • Shine “white” light onto hydrogen atom White light Photons/sec Wavelength

24. Photons/sec 660 nm Wavelength The Physics of Light • Spectroscopy and Atomic Physics • Only photons with energy equal to energy difference • between orbits 2 and 3 are absorbed. This energy • corresponds to a wavelength of 660 nm.

25. Photons/sec 660 nm Wavelength The Physics of Light • Spectroscopy and Atomic Physics • Photons with energy equal to energy difference • between orbits 2 and 3 are emitted. These photons • are emitted in all directions.

27. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws

28. The Physics of Light • Spectroscopy and Atomic Physics • Energy Level Diagrams Ground State