1.  Spectroscopy continued 
Topic 3 Part II
 Spectroscopy continued 

2. Clarification
Close your eyes while I read you a story about how waves and light work
NOTE:
A wave is a way of transferring energy through a medium of some kind.

3. Diffraction Gratings
Spectroscopes usually use prisms to split the light into a spectrum.
To get the best detail in a spectrum, a diffraction grating can be used instead of a prism.

4. When light is passed through VERY small openings, a spectrum is produced.
This happens because the waves bend around corners and diffract (bend)
A device with thousands of closely spaced slits is called a diffracting grating

5. Examples of where diffraction gratings are used:
CD’s
Holographic trading cards

6. Spectroscopy for Astronomers
Review – THREE TYPES OF SPECTRA
1. Emission (Bright Line) Spectrum
2. Continuous Spectrum
3. Absorption (Dark Line) Spectrum

7. You should have saw in the stations lab that different sources of light produce different types of these spectra.
Also, you know that Kirchoff and Bunsen discovered that each element (when heated in a vacuum) produces a unique pattern of spectral lines.

8. Solar Spectrum
A light that passes through a gas will have spectral lines (dark) where the gas has absorbed the light.
The solar spectrum had HUNDREDS of dark lines which means the light had to have passed through several gases in the sun’s atmosphere before reaching Earth

9. Spectral Analysis
By looking at each of these dark lines in the solar spectrum, we can determine which elements are present in the Sun’s atmosphere.
COOL!!

10. Example
Hydrogen
Helium
Sodium
Star 1
Star 2