Spectra Light from stars can be spread into a spectrum by a prism, spectroscope,

Question

Spectra Light from stars can be spread into a spectrum by a prism, spectroscope, or other device. The colors typically go along with wavelengths, measured in nanometers (nm), as shown below 400 500 600 700 ? (nm) Image From Davidson.edu (http://www.chm.davidson.edu/vce/coordchem/color.html) 1. Look up the emission spectra for hydrogen, helium, neon, and mercury. Emission information in this youtybe video (http:1/www.youtube.com/watch? QI50GBUJ48s), this ucick site (http:/www ucolick.org/-bolte/AY4 00/week2/stellar tempsC.html), and video (http://www.youtube.com/watch?v=Va2F1 e7ViKw). a) What is an emission spectrum? b) For each gas, list the main colors in its emission spectrum. c) For hydrogen, what are the approximate wavelengths corresponding to these colors? d) Which two of these elemental gases would you expect to find in large amounts in

Explanation / Answer

(a) When energy is supplied to an atom, electrons gain energy and jump to higher energy levels from ground state to an excited state. However, they can't remain at excited state so they drop to lower levels and emit energy. The energy emitted corresponds to a wavelength and shows up as a line in the spectrum. This is called emission spectum. It will looks as a black background with coloured lines where transitions take place.

(b) Hydrogen - Red, Blue-Green, Blue-Violet, Violet

     Helium - Yellow,Blue, Green

   Neon - Red ,Pink, Green

   Mercury - Greenish colour and Blue.

(c) For hydrogen, red line -656nm

                         blue green line-486nm

                         blue line -434nm

                       violet line -410nm

(d) Hydrogen and helieum elemental gasses are in large amounts in the atmospheres of stars.

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