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Fill In The Blank Notes



Electrons give off light when they return to the ground state after being excited by an energy source



Bohr studies the light given
off by a 'Black Body'



Neils Bohr, right



'Black Body' = heated body that gives off only the light from its internal glow - no reflected light


Material was heated and the light
 given off was analyzed






School blocks YouTube? Click below

| Onsite Version |

St. Mary's U. Astronomy and Physics Dept.


Spectral lines
Physics 2000

Emission Spectra


Whatever colors an element gives off, it also .....







... absorbs


Atomic Spectra
University of Oregon 


Atomic Spectra for Iron



Full Spectrum


Hydrogen Emission
/Absorption Spectrum

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Place your mouse over the image to see the absorption spectra



Full Spectrum





Place your mouse over the image
to see the absorption spectra

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Every Energy level transition creates a single spectral line



| Onsite Version |




"Science of the Silicon Solar Cell"

Don Ion



How many different spectral lines can be produced
by an atom with 5 energy levels?










10 Spectral Lines



10 colors



10 frequencies

10 photons






Black Body Radiation Results:


1. Only the high energy objects gave off colors on the violet side of the spectrum 








Low Frequency


High Frequency


Frequency related to Energy




2. Electrons in atoms are not capable of giving off all colors (energies)




3. Each element gives off a unique pattern of colors called a 'bright line spectrum'.



  This knowledge is very useful to chemists and other scientists. Why?





 1. Spectral lines used to:


  • identify unknown elements.


  • determine the composition of distant stars







To Identify an Unknown Element



- Electrify, Heat it up and analyze its colors.


- Compare emitted colors to a database of elemental spectral lines








The diagram below represents the bright-line spectra of four elements, A, B, C, and D, and the spectrum of an unknown gaseous sample.

Based on comparisons of these spectra,
which two elements are found
in the unknown sample?

Jan 2006




B and C


What are stars made of ?





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