The Prism : The prism fascinated me in school. I wondered how it would 'break' up light into it's constituent colors. That was what we were taught. But of course, there is so much more to why that happens. White light is not 'pristine'... it already has all the colors. In fact the colors are part of white light. To understand this, one has to ask 'what is color'. Color is nothing but our perception of the different wavelengths of light. Our perception of color is not the same as the perception of color which a mantis shrimp has for example (which sees much more of the EM spectrum than us) or a cat (which sees less of the spectrum than humans).
Of course the prism is just glass (or some transparent material). It sits on a triangular base and has rectangular sides. In school I imagined it was some special material !
Refraction and speed of light in materials : Refraction simply means that light travels at a different speed in different materials. It's fast in air, and slower in water or glass. This has the effect of changing the direction of light, or bending it, when it moves from one material to the other.
But why do different colors go in different directions? This is because different colors of light travel at different speeds in the glass. So from the analogy above, slower speeds in the glass make the light bend more. We call this effect dispersion, since it disperses the colors in different directions. Blue light travels slightly slower in glass than red light, so it bends a sharper angle when it enters the glass from air. In physics, we say the glass has a higher refractive index for blue light than red light. There is a formula (Snell's Law) that you can use to calculate angles from refractive index, or the other way around.
How refraction actually works (Quantum Electrodynamics) : Another way to answer this is through QED which talks about how light interacts with atoms of the material it is traversing. I will not even attempt to explain this here. But Richard Feynman got a nobel prize in Physics explaining the phenomenon. See Richard Feynman Lecture on Quantum Electrodynamics: QED. 1/8 . You can even get his book and read about it.
Article Source: http://scienceline.ucsb.edu/getkey.php?key=1542
Reference: http://en.wikipedia.org/wiki/Prism
Additional reference: http://en.wikipedia.org/wiki/Optics
'The strange theory of light' : http://qed.wikina.org/refraction/
Ask a scientist : http://www.newton.dep.anl.gov/askasci/phy00/phy00612.htm
Additional source: http://www.nevis.columbia.edu/~conrad/classes/QED4.html
Earlier post 'How we perceive color' : http://goo.gl/g5b7Xb
Pic courtesy: From Wikipedia
Of course the prism is just glass (or some transparent material). It sits on a triangular base and has rectangular sides. In school I imagined it was some special material !
Refraction and speed of light in materials : Refraction simply means that light travels at a different speed in different materials. It's fast in air, and slower in water or glass. This has the effect of changing the direction of light, or bending it, when it moves from one material to the other.
But why do different colors go in different directions? This is because different colors of light travel at different speeds in the glass. So from the analogy above, slower speeds in the glass make the light bend more. We call this effect dispersion, since it disperses the colors in different directions. Blue light travels slightly slower in glass than red light, so it bends a sharper angle when it enters the glass from air. In physics, we say the glass has a higher refractive index for blue light than red light. There is a formula (Snell's Law) that you can use to calculate angles from refractive index, or the other way around.
How refraction actually works (Quantum Electrodynamics) : Another way to answer this is through QED which talks about how light interacts with atoms of the material it is traversing. I will not even attempt to explain this here. But Richard Feynman got a nobel prize in Physics explaining the phenomenon. See Richard Feynman Lecture on Quantum Electrodynamics: QED. 1/8 . You can even get his book and read about it.
Article Source: http://scienceline.ucsb.edu/getkey.php?key=1542
Reference: http://en.wikipedia.org/wiki/Prism
Additional reference: http://en.wikipedia.org/wiki/Optics
'The strange theory of light' : http://qed.wikina.org/refraction/
Ask a scientist : http://www.newton.dep.anl.gov/askasci/phy00/phy00612.htm
Additional source: http://www.nevis.columbia.edu/~conrad/classes/QED4.html
Earlier post 'How we perceive color' : http://goo.gl/g5b7Xb
Pic courtesy: From Wikipedia
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