Doppler Effect - San Francisco State...

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Doppler Effect

Transcript of Doppler Effect - San Francisco State...

Page 1: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

Doppler Effect

Page 2: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

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

~

Page 3: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

Shane 3meterTelescope,Mt. Hamilton

Page 4: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

CCD LightDetector

DiffractionGrating

Collimator

StarlightFrom Telescope

Keck ObservatoryHigh Resolution Spectrometer

Page 5: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

Doppler Effect makes spectral lines shift

Page 6: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

Doppler Effect makes spectral lines shift

Doppler shift exaggerated 374,000 times!

Page 7: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

Spectrum of Hydrogen

These numbers have a pattern:

Eq on board

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

Page 8: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

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

Page 9: Doppler Effect - San Francisco State Universityphysics.sfsu.edu/~chris/astro300/lectures/lect16.pdfDoppler Effect Proper motion can be measured by observing a star’s location for

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....