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Why does violet light bend more than red light? Is there a more intuitive reason than just using formula to explain?
chromatic dispersion
- Thread starter yjj8817
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The reason I remember is conservation of energy propagated per second: since violet light is more energetic, if it traveled at the same speed through the medium as red light it would propagate more energy through that same path than the red light; so we need to slow down the violet light more than the red light, and this is achieved by giving the violet light a larger index of refraction (in other words a larger barrier to propagation). A "side effect" of this is the increased bending of violet light compared to red light.
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Violet light bends more than red light (or any light of a lower frequency for that matter) due to the inherent properties of matter as light passes through, the physical basis for this is quantum mechanical and I do not pretend to understand it adequately enough to explain it. However, I can explain it for the scope of the MCAT.
The index of refraction for a particular material depends on the wavelength of light passing through it.
(As a side that you probably already know: The speed of light in a vacuum is the same for all wavelengths of electromagnetic radiation.)
In most materials with some degree of transparency, the index of refraction, n, decreases with a decrease in frequency and an increase in wavelength, and vice versa: the index of refraction increases with an increase in frequency and decrease in wavelength.
This means that in such a material light with a longer wavelength will actually have a greater speed than light of a shorter wavelength.
This causes violet light to deviate more from its path than red light would, as the index of refraction is greater. The equation for the deviation from original path is pretty complicated, but if you're interested you can definitely find it online.
But you can think about it generally with Snell's Law, law of refraction: n1sin(A1)=n2sin(A2).
I would encourage you to think about a prism and how Snell's Law might be generally applied to show that A2 for blue light is greater than A2 for red light as both lights enter the prism (keep in mind that there is 1 refractive event happening when the lights enter the prism, and another when the lights leave).
The index of refraction for a particular material depends on the wavelength of light passing through it.
(As a side that you probably already know: The speed of light in a vacuum is the same for all wavelengths of electromagnetic radiation.)
In most materials with some degree of transparency, the index of refraction, n, decreases with a decrease in frequency and an increase in wavelength, and vice versa: the index of refraction increases with an increase in frequency and decrease in wavelength.
This means that in such a material light with a longer wavelength will actually have a greater speed than light of a shorter wavelength.
This causes violet light to deviate more from its path than red light would, as the index of refraction is greater. The equation for the deviation from original path is pretty complicated, but if you're interested you can definitely find it online.
But you can think about it generally with Snell's Law, law of refraction: n1sin(A1)=n2sin(A2).
I would encourage you to think about a prism and how Snell's Law might be generally applied to show that A2 for blue light is greater than A2 for red light as both lights enter the prism (keep in mind that there is 1 refractive event happening when the lights enter the prism, and another when the lights leave).
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