Solar Spectrum

Bit of Administration …. c = 3 x 10 8 m/sec = 3 x 10 5 km/secc = 3 x 10 8 m/sec = 3 x 10 5 km/sec Reading Reading –BSNV pp

The Physics of Light Doppler Shift Doppler Shift

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

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

The Physics of Light Doppler Shift Doppler Shift v rad = radial velocity of light source or observer (+ => away from each other) (+ => away from each other)  = change (shift) in wavelength = observed - rest rest = rest wavelength rest = rest wavelength c = 3 x 10 5 km/sec

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

The Physics of Light Light as a Particle = Photons Light as a Particle = Photons Photon - A Discrete Unit of Light Energy Photon - A Discrete Unit of Light Energy Planck’s Law Planck’s Law h = Planck’s Constant = x joule sec = wavelength in m, c = 3 x10 8 m/sec

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

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

The Physics of Light Spectroscopy and Atomic Physics Spectroscopy and Atomic Physics Kirchoff’s Laws Kirchoff’s Laws 1. An opaque object emits a continuous spectrum. 2.An opaque object viewed through a cooler gas will produce an absorption spectrum. 3.A gas viewed against an empty background produces an emission spectrum

The Physics of Light Spectroscopy and Atomic Physics Spectroscopy and Atomic Physics Kirchoff’s Laws Kirchoff’s Laws

The Physics of Light Spectroscopy Spectroscopy Temperature - a measure of the speeds of particles Temperature - a measure of the speeds of particles Room Temperature 300 o K

The Physics of Light Spectroscopy Spectroscopy Thermal Radiation - Any opaque object that has a Thermal Radiation - Any opaque object that has a temperature above 0 o K emits light temperature above 0 o K emits light

The Physics of Light Spectroscopy Spectroscopy Thermal Radiation Thermal Radiation

The Physics of Light Spectroscopy Spectroscopy Thermal Radiation Thermal Radiation

The Physics of Light Spectroscopy Spectroscopy Thermal Radiation Thermal Radiation Wien Law Wien Law max in nm T in o K max max

The Physics of Light Spectroscopy Spectroscopy Thermal Radiation Thermal Radiation Wien Law Wien Law Stefan-Boltzmann Law Stefan-Boltzmann Law  Stefan-Boltzmann constant  flux  energy emitted from square meter in one second

The Physics of Light Spectroscopy and Atomic Physics Spectroscopy and Atomic Physics Kirchoff’s Laws Kirchoff’s Laws

The Physics of Light Spectroscopy and Atomic Physics Spectroscopy and Atomic Physics Quantum Mechanics - Electron can only be in certain specific Quantum Mechanics - Electron can only be in certain specific orbits can only have certain specific energies orbits can only have certain specific energies QuantumNumbers e HydrogenAtom

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

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

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

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

The Physics of Light Spectroscopy and Atomic Physics Spectroscopy and Atomic Physics Kirchoff’s Laws Kirchoff’s Laws

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