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The Physics of Rainbows

To prove that the sun is emitting light of different frequencies,  point a spectral scope towards the sunlight outside (see Figure 6).  You should be able to see the seven colours.  You should also be able to see several distinct and significantly brighter lines.  These make up the sun's emission spectrum. 

Next, you should try pointing the spectroscope at another  light source to test if its spectrum is continous.  Try a fluorescent light tube!  A better quality spectral scope should also tell you the wavelength of the various colours.  Using the spectralscope, you can now find out the wavelengths of the different colours you see.  You can then try to calculate their respective frequencies.

But not ALL light source gives out a continous spectrum.  Try pointing the spectral scope at a laser beam projected onto a wall.  Instead of the beautiful colours you saw a while earlier, all you will see is a red dot.  This is because laser is not a continous light source.  Try an incandescent light bulb!  Do you see any gaps?


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