Index of refraction of various colors

[EECStoMed]

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So apparently light of a higher frequency, smaller wavelengths have a larger index of refraction. In other words, blue light bends more towards the normal when it enters a medium than red light. So my question is, when it exits the glass, why isn't it a rainbow color? But rather white, which is a mix of all wavelengths?

 

[vicinihil]

From a perfect prism, it is a rainbow color. You see the seperation perfectly. Com'on man don't you own a PERFECT prism, I mean everyone has one. That's what all the cool kids have.

 

[Chargers]

I am not sure about this one but I think it's because of the different media. When you shine a white light into a glass surface, it goes from air to glass. When it exits, it goes from glass into air again. So if it's white in air medium, it should be white in air medium when it exits. It should be a rainbow color in the glass medium. Someone correct me please.

 

[EECStoMed]

I am not sure about this one but I think it's because of the different media. When you shine a white light into a glass surface, it goes from air to glass. When it exits, it goes from glass into air again. So if it's white in air medium, it should be white in air medium when it exits. It should be a rainbow color in the glass medium. Someone correct me please.

Well a prism doesn't do that. It goes from air to glass then air.

 

[BrokenGlass]

So apparently light of a higher frequency, smaller wavelengths have a larger index of refraction. In other words, blue light bends more towards the normal when it enters a medium than red light. So my question is, when it exits the glass, why isn't it a rainbow color? But rather white, which is a mix of all wavelengths?

Because the 2 interfaces for a glass (i.e. the kind of glass used for windows) are PARALLEL to each other. In a prism, the 2 interfaces are not parallel, that's why we get chromatic disperson.

 

[EECStoMed]

Because the 2 interfaces for a glass (i.e. the kind of glass used for windows) are PARALLEL to each other. In a prism, the 2 interfaces are not parallel, that's why we get chromatic disperson.

Even if the glass is extremely thick?

 

[J ROD]

Because the 2 interfaces for a glass (i.e. the kind of glass used for windows) are PARALLEL to each other. In a prism, the 2 interfaces are not parallel, that's why we get chromatic disperson.

You really know your Physics. How did you learn it?

Just natural ability after taking the courses or did you use a particular prep source?

It's my problem area and I want to improve.. THanks,

 

[BrokenGlass]

You really know your Physics. How did you learn it?

Just natural ability after taking the courses or did you use a particular prep source?

It's my problem area and I want to improve.. THanks,

2 words m'friend: Berkeley Review.

 

[BrokenGlass]

Even if the glass is extremely thick?

Yes. As long as 2 intefaces are parallel, there will be no chromatic disperson because the bending and "un"bending will cancel each other out at 2 interfaces.

 

[EECStoMed]

2 words m'friend: Berkeley Review.

Umm, yea, great. Thank you.

 

[EECStoMed]

Yes. As long as 2 intefaces are parallel, there will be no chromatic disperson because the bending and "un"bending will cancel each other out at 2 interfaces.

If you have a very thick glass, wouldn't it separate within to the point where you can see the different colors. On top of that, as it appears on the other side, it wouldn't be able to add up together again.

 

[J ROD]

2 words m'friend: Berkeley Review.

Thank you.

I guess I need to look more into those books.

Have you ever seen TPR books?

Is all of TBR good or just the PS?

 

[EECStoMed]

Thank you.

I guess I need to look more into those books.

Have you ever seen TPR books?

Is all of TBR good or just the PS?

I have the TPR book and it says nothing about this. Neither does EK.

 

[FlowLimited]

Yes. As long as 2 intefaces are parallel, there will be no chromatic disperson because the bending and "un"bending will cancel each other out at 2 interfaces.

Actually, if the glass is sufficiently thick, dispersion will come about even if the interfaces are parallel. Dispersion is governed not only by the index of refraction and angle of incidence, but also by the thickness of the material. Therefore, if you have an especially thick piece of material, you will have dispersion.

 

[BrokenGlass]

Actually, if the glass is sufficiently thick, dispersion will come about even if the interfaces are parallel. Dispersion is governed not only by the index of refraction and angle of incidence, but also by the thickness of the material. Therefore, if you have an especially thick piece of material, you will have dispersion.

Could be. Btw, how thick is sufficiently thick?

 

[BrokenGlass]

Thank you.

I guess I need to look more into those books.

Have you ever seen TPR books?

Is all of TBR good or just the PS?

I haven't seen TPR books, but I know people who scored in the 99% just by using TPR books. No book could possibly have anything and everything you may see on the MCAT. I have only seen EK and TBR books. EK is good for drilling in the basic concepts and formulas (I listen to AO every day for 2 hours because I have a long commute to and from work). BR has good passages and good explanations even if you don't read the book chapters. I actually did read all the chapters in all the BR books. I took TBR course in Los Angeles. BerkReviewTeach taught most of my classes. I don't think there is any anybody in the country who knows more about MCAT (and/or has more experience with MCAT) than he does. So needless to say, going to class was very helpful.

IMO, the hardest part about MCAT is the volume of information covered. No one topic is particularly challenging. BR course consisted of 38 science lectures + verbal + other lectures... On the real MCAT, I will be tested on at most 14 science topics. So there is always a lot of luck involved in getting a good score... Will I get the passages on topics I know best or not? That remains to be seen, but luck is definitely a HUGE factor.

 

[FlowLimited]

Could be. Btw, how thick is sufficiently thick?

Well in actuality, light passed through any thickness material will experience dispersion. The key is whether it is visually observable and that's where the issue of thickness is important.

Light is always slightly offset when it passes through a material, which is why objects appear slightly displaced when you view them through a glass slab. With materials with approximately parallel interfaces, the dispersion is only apparant at the edges due to the offset. The phenomenon is not easily observable because, unlike with a prism, the direction of the light remains unchanged.

 

[BrokenGlass]

Well in actuality, light passed through any thickness material will experience dispersion. The key is whether it is visually observable and that's where the issue of thickness is important.

Light is always slightly offset when it passes through a material, which is why objects appear slightly displaced when you view them through a glass slab. With materials with approximately parallel interfaces, the dispersion is only apparant at the edges due to the offset. The phenomenon is not easily observable because, unlike with a prism, the direction of the light remains unchanged.

So how thick should the glass be for dispersion to be "visually observable" with a naked eye 🙂 Assume parallel interfaces.

 

[FlowLimited]

So how thick should the glass be for dispersion to be "visually observable" with a naked eye 🙂 Assume parallel interfaces.

Well that depends on your vision. 😀 The point, however, is that while inside a medium, the different wavelengths will split. This is not a phenomenon specific to only prisms. As they emerge again, all the colors will be redirected and so the angle of the light will not change but the wavelengths will still exit at slightly different locations due to the splitting. What you'll observe will be a beam of white light but with one slightly red edge and one slightly blue edge. A thicker material will allow the beam to split more before it is recombined and therefore the effect will be greater.

 

[BrokenGlass]

Well that depends on your vision. 😀 The point, however, is that while inside a medium, the different wavelengths will split. This is not a phenomenon specific to only prisms. As they emerge again, all the colors will be redirected and so the angle of the light will not change but the wavelengths will still exit at slightly different locations due to the splitting. What you'll observe will be a beam of white light but with one slightly red edge and one slightly blue edge. A thicker material will allow the beam to split more before it is recombined and therefore the effect will be greater.

You must have been looking through some mighty thick glass pieces.

 

[FlowLimited]

You must have been looking through some mighty thick glass pieces.

Well yeah, we aren't talking microscope slides or anything. I was just trying to clear up the misconception that dispersion only exists when non-parallel interfaces are involved.