How does refraction really work

In summary: If you know any of the answers to these questions, please help him. In summary, Dave learned that light does not "bend" when slowed down, that different wavelengths are refracted to different degrees, and that different materials can slow light down without being dispersive.
  • #1
peter.ell
43
0
I've looked into refraction and diffraction of light, but there are a few things that I don't understand, if you know any of the answers to these questions, please help me:

1.) Why does light bend when it slows down instead of just continuing on in the same direction after being absorbed, held, and then emitted by the electrons in the medium? Why don't the electrons emit the light in the same direction after they absorb it? And how does simply increasing the delay between absorption of light and emission of light cause it to bend more? This doesn't make much sense.

2.) Why are different wavelengths of light refracted to different degrees? I know it's because different wavelengths are slowed to different degrees, but what causes this? Aren't different wavelengths absorbed or transmitted depending on how the electrons in a specific material interact with each wavelength of light, yet all transparent materials slow blue light more than red light, why? What causes does one wavelength travel slower than another?

3.) What's the difference between a dispersive medium and a non-dispersive medium? How can some materials slow light down without being dispersive?

4.) How is it possible for the colors of a rainbow to be so pure? Given what I learned about the light paths for different colors in a rainbow, I know that red light is not only refracted at the angle where red is seen in a rainbow, but also at all the other angles. Given this, it means that, while green light is not refracted at the top of a rainbow where red is, red happens to be refracted where green is... which should mean that we would not be able to see any of the colors in a rainbow except for red and whatever the combination of red and all the other colors turns out to be. Yet we don't, why not?

My utmost thanks for helping me understand these questions!
 
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  • #2
Light does not "bend" when "slowed down"
The medium might "bend" the totality of a photons passage, but the light itself does not bend.

Think of a car in a curve. The path bends but the car does not. The car follows the path, giving an illusion of bend.
 
  • #3
ok that's an interesting answer

since this "illusion" is a physically measurable quantity. what is the meachanism in the material, say glass, that is occurring ?

Dave
 
  • #4
Right. That is a question more suited for the experts(or the FAQ"S section) than I.
 
  • #5
http://www.vega.org.uk/video/subseries/8
You might want to watch the Feynman lectures on light.
And light has momentum so that might be why blue light takes a different angle in glass than red light.
And you can get the refracted angle and reflected angle by applying Maxwells equations to the material and it will depend on
[tex]
\epsilon [/tex] and [tex] \mu [/tex] for that material
 
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  • #6
Thanks Cragar listening to those lectures now have heard many of his ones over the years. a very brilliant guy huh !

Dave
 

1. How does light bend when it passes through different mediums?

Refraction occurs when light passes through a medium with a different density than the medium it was traveling through. The change in density causes the light to slow down and change direction, resulting in a bending of the light.

2. What is the cause of refraction?

The cause of refraction is the change in speed of light as it passes through different mediums. This change in speed is due to the change in density, which affects the wavelength and direction of the light.

3. Why does a pencil appear bent when placed in a glass of water?

This is due to the refraction of light. When light enters the water from air, it slows down and bends towards the normal line (an imaginary line perpendicular to the surface of the water). When the light exits the water, it speeds up again and bends away from the normal line. This change in direction is what makes the pencil appear bent.

4. Does refraction only occur with visible light?

No, refraction can occur with all types of electromagnetic radiation, including radio waves, microwaves, infrared, ultraviolet, and X-rays. However, the amount of refraction varies depending on the wavelength of the light.

5. Why does a prism separate white light into different colors?

A prism separates white light into different colors because each color of light has a different wavelength and therefore, a different index of refraction. As the light passes through the prism, each color bends at a different angle, causing them to separate and create a rainbow effect.

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