Doppler Effect

Doppler Effect

Proper motion can be measured by observing a star’s location for several years.

Radial velocity is usually measured using the Doppler effect.

Δλ

Δλ

~

Shane 3meterTelescope,Mt. Hamilton

CCD LightDetector

DiffractionGrating

Collimator

StarlightFrom Telescope

Keck ObservatoryHigh Resolution Spectrometer

Doppler Effect makes spectral lines shift

Doppler Effect makes spectral lines shift

Doppler shift exaggerated 374,000 times!

Spectrum of Hydrogen

These numbers have a pattern:

Eq on board

They are the wavelengths (in nm) of the spectral lines of Hydrogen.

Spectrum of Hydrogen

Observations of Hydrogen in a lab show it gives off light of specific wavelengths, given by the empirical formula:

...where n & m are integers & RH = 1.1 x 107 m-1

Eq on board

Electron ‘orbits’ nucleus under the electrical force, F, & potential energy, U

Assuming uniform circular motion:

Hydrogen Atom in Classical Physics

Newton’s 2nd Law, (F = m a), gives expressions for: -kinetic energy of the electron. -total energy

But the emission line spectrum of Hydrogen is still not explained....