http://en.wikipedia.org/wiki/Energy_level [2]
http://www.ualberta.ca/~pogosyan/teaching/ASTRO_122/lect5/lecture5.html [3]
http://hyperphysics.phy-astr.gsu.edu/hbase/bohr.html [4]
http://skepticsplay.blogspot.in/2008/09/why-is-quantum-discrete.html [5]
http://uw.physics.wisc.edu/~himpsel/107/Lectures/Phy107Lect25.pdf [6]
Links
[1] https://www.hootsgo.org/?q=node/6399
[2] http://en.wikipedia.org/wiki/Energy_level
[3] http://www.ualberta.ca/~pogosyan/teaching/ASTRO_122/lect5/lecture5.html
[4] http://hyperphysics.phy-astr.gsu.edu/hbase/bohr.html
[5] http://skepticsplay.blogspot.in/2008/09/why-is-quantum-discrete.html
[6] http://uw.physics.wisc.edu/~himpsel/107/Lectures/Phy107Lect25.pdf