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From "Astronomy! A Brief Edition," J. B. Kaler, Addison-Wesley, 1997.

Slide 11

Kirchhoffs Laws Cont

Kirchhoffs Laws Cont

Excited electrons, dont stay excited forever.

Drop back down to their ground floors.

Only light of the precise energy difference between floors is given off.

This light goes off in all directions.

From a second detector, we see these specific energy wavelengths: an emission spectrum.

Slide 12

Continuum, Absorption, Emission

Continuum, Absorption, Emission

Slide 13

Spectral Lines

Spectral Lines

Heat low density gas and it will glow.

Pass the light through a slit to get a narrow source.

Pass light from the slit through a prism.

Get multiple images of the slit, each at a different wavelength.

These lines are the elements finger print.

Spectrometer

Slide 14

Emission Lines

Emission Lines

Every element has a DIFFERENT finger print.

Slide 15

Multiple elements

Multiple elements

Gases, stars, planets made up of MANY elements have spectra which include ALL of the component spectral lines.

Its the scientists job to figure out which lines belong to which element.

Slide 16

Different stars, different spectra

Different stars, different spectra

Different stars have different types of spectra.

Different types of spectra mean different stars are made of different elements.

Hot

Cool

Stellar Spectra

Annals of the Harvard College Observatory, vol. 23, 1901.

Slide 17

To Sum Up

To Sum Up

EVERY element has a SPECIAL set of lines.

Atoms fingerprint.

Observe the lines and you identify the component elements.

Identify:

Absorption spectrum

Emission emission

Learn about the environment of the element

Slide 18

Concept Test

Concept Test

The sunlight we see is thermal radiation caused by the extreme heat of the suns surface. However, the very top thin layer of the suns surface is relatively cooler than the part below it. What type of spectrum would you expect to see from the sun?

A continuous spectrum.

A continuous spectrum plus a second, slightly redder continuous spectrum.

A continuous spectrum plus a second slightly bluer continuous spectrum.

A continuous spectrum plus an emission spectrum.

A continuous spectrum plus an absorption spectrum.

Slide 19

The Sun

The Sun

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