chapter 5.5 formation of spectral lines & 5.6 the doppler effect

electron orbitals

each type of atom has its own unique pattern of electron orbits, and no two sets of orbits are exactly alike

• each type of atom shows its own unique set of spectral lines, produced by electrons moving between is unique set of orbits

ground state

an atom is in the state of lowest possible energy

• in the Bohr model of the hydrogen atom, the ground state corresponds to the electron being in the innermost orbit

excitation

when an atom absorbs energy, to raise it to a higher energy level

• the atom is said to be in an excited state

• generally an atom only remains excited for only a very brief time

ionisation

occurs when an electron can be completely removed from an atom

• occurs during an excited state

• creates an ion

• if enough energy is available, the atom can be completely ionised, losing all of its electrons

• The rate at which such collisional ionisations occur depends on the speeds of the atoms and hence on the temperature of the gas—the hotter the gas, the more of its atoms will be ionised

• depends on the density of the gas

doppler effect

• an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other

• The effect causes the sudden change in pitch noticeable in a passing siren, as well as the red shift seen by astronomers

• produced only by a motion toward or away from the observer, called radial velocity

blueshift

When the source of waves moves toward you, the wavelength decreases a bit.

• If the waves involved are visible light, then the colors of the light change slightly.

• As wavelength decreases, they shift toward the blue end of the spectrum

redshift

When the source moves away from you and the wavelength gets longer

doppler effect formula