Absorption and Emission Spectra
From High School Online Collaborative Writing
Contents |
[edit] Dispersion of a Spectra
As proven in Bohr’s Model of the atom, isolated atoms can absorb and emit packets of electromagnetic radiation. When light passes through a prism or spectrograph it is separated according to wavelength:
If you look at the diagram you can see a single white light, which is refered to as polychromatic, is shone through the prism. This white light is then separated into six colors or components: Violet, Blue, Green, Yellow, Orange, Red.
This phenomenon is known as dispersion. It occurs because the speed of light in the prism depends on the color of the light passed through.By looking at the order of the dipersion of light, red would be the fastest while violet is slowest light ray.
[edit] Electromagnetic Spectrum
Light is essentially an electromagnetic wave. This diagram below shows all the different forms of light. Electronmagnetic waves differ in frequency and looking specifically at the visble portion of the diagram the amount of frequency could be directly related to the speed of the light ray.
[edit] Absorption Spectrum
An absorption spectrum occurs when light passes through a cold gas. The atoms in the gas then absorb at certain characteristic frequencies. This happens since the re-emitted light is probably unlikely to be emitted in the same direction as the absorbed photon. This gives rise to dark lines (absence of light) in the spectrum.
[edit] Emission Spectra
Emission spectra are produced by thin gases in which the atoms do not experience many collisions as a result of the low density. The emission lines show photons of rather undetectable energies that are emitted when excited atomic states in the gas change back to lower energy levels.
[edit] Absorption and Emission Spectra
[edit] References
• Bolte, Michael “Continuum, Absorption & Emission Spectra” http://astronomy.nmsu.edu/nicole/teaching/ASTR110/lectures/lecture19/slide02.html
• Himanshu, 2006 http://answers.yahoo.com/question/?qid=1006042911794
• http://csep10.phys.utk.edu/astr162/lect/light/absorption.html
[edit] Picture References
1. http://csep10.phys.utk.edu/astr162/lect/light/absorption.html
2. http://universe-review.ca/Frame.htm
3. http://www.wwnorton.com/college/chemistry/chemconnections/BlueLight/pages/elements.html
4. http://www.wwnorton.com/college/chemistry/chemconnections/BlueLight/pages/elements.html
5. http://www.wwnorton.com/college/chemistry/chemconnections/BlueLight/pages/elements.html
