The hydrogen atom Energy is measured in eV, or electron volts Light (photon) is electromagnetic energy Since only permitted electron orbits (energies), there are only permitted photon energies that interact with the atom. The photon energy equals the energy difference of the electron orbits (not shown) (true colors) Energy = 12.8 – 10.2 = 2.6 eV

n=1 n=3 n=2 Energy Increasing

Lyman Balmer Paschen Balmer Series

Blackbody Radiation max = 3,000,000 T nanometer E total = constant x T 4 J/s/m 2 E total = area under BB curve T = absolute temperature Absolute temperature measures the internal kinetic energy of an object. This is the energy from all the motions of the atoms.

Absolute Temperature Units = Kelvins Measures kinetic energy (motion and/or speed) of particles in a gas, solid, or a liquid Shown below is a gas … cooler hotter

Stars have absorption spectra.

Stellar spectrum showing hydrogen absorption.

Ionization is the removal of an electron from an atom by a very high energy photon Electron is “kicked” off the atom by a photon with E > 13.6 eV (in this case- for hydrogen atom) The resulting atom is called an ion and it has totally new electron orbits/energies. Thus, the spectral lines are completely different. E = Energy

BB just right.BB too hot. hydrogen ionized. BB too cool. BB = blackbody (spectrum). ionized atoms (ions) excited atoms ground-state atoms

Different atoms have different temperature dependencies because energy needed to ionize them is different.

Finally, to get temperature… use many ions. At any given temperature, some atoms are in ground state, some excited (creating absorption lines), and some ionized (creating absorption different lines from same element).

Spectral Class or Type Historically by Key Absorption Features Now Understood as a Temperature Sequence O, B, A, F, G, K, M coolerhotter

The Doppler Shift (light). BLUE SHIFT Higher frequency Higher energy Shorter wavelength RED SHIFT Lower frequency Lower energy Longer wavelength

The Doppler Shift (sound). Higher pitchLower pitch

REDSHIFREDSHIF BLUESHIFBLUESHIF

MID TERM EXAM 1 WEDNESDAY FEBRUARY 6 USUAL TIME All LECTURED MATERIAL AND READING ASSIGNMENTS BUT NOT GRAVTITY AND KEPLERS LAWS