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Thread: Rainbow '"Internal Refraction"?

  1. #1 Rainbow '"Internal Refraction"? 
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    http://www.youtube.com/watch?v=2kBOqfS0nmE

    T
    he above link, is of a total internal refraction.

    At 3.08 minutes you can see the total internal refraction.

    raindrop.jpg


    Above is the refraction of light in a raindrop, a picture I downloaded via the internet.




    Question 1 - Why is it , that the raindrops , do not have a totally internal refraction, as in the underwater refraction. Is this because of the angle of the incident ray?.



    Question 2 - When the raindrop is falling, and light is refracted through the rain drop, displaying our "rainbow", spectrum of color. Why is it that the perspective view of a ''rainbow", " stays in the same place", relative to the observer, the "rainbow doe's not move"?.


    Question 3 - Can a "rainbow", be formed , by diffraction, "off a wet surface"?.


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  3. #2  
    Genius Duck Dywyddyr's Avatar
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    Still clueless I see.
    There's no such thing as "total internal refraction".
    It is physically impossible.
    Learn to use the correct words.


    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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  4. #3  
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    Quote Originally Posted by Dywyddyr View Post
    Still clueless I see.
    There's no such thing as "total internal refraction".
    It is physically impossible.
    Learn to use the correct words.
    I thank you for answering question 1.

    Do you have any answers for 2 and 3?
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  5. #4  
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    Quote Originally Posted by PhDemon View Post
    Total internal reflection - Wikipedia, the free encyclopedia

    not total internal refraction.

    Q1. Raindrops do show total internal reflection, you even posted a picture of it.
    Q2. It is not always the same droplets you are seeing, where you see the rainbow depends on the angle of the sun it is roughly 42 degrees of the axis of sunlight - you will only see a rainbow when droplets are at this angle as there if there is a constant supply of doplets falling through this angle you see a rainbow.

    Rainbow Angles (Physics of Rainbows) has a picture

    Q3 no, the total internal reflection like this only works in spherical particles.
    I thank you for the link on the Physics of a rainbow, that is much more informative.


    Q3 - I did not mean internal refraction, If a surface is wet, e.g a road, and the sun was at the 42 degrees angle, is it possible for light to diffract off the road, similar to a Cd , off the wet layer?
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  6. #5  
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    Quote Originally Posted by PhDemon View Post
    no because for total internal reflection the light reflects of the back of the rain drop, this can't happen on a wet road...
    I thank you , but I still do not think you understand my question, I will re-word it.

    A cd diffracts light, so would a wet surface have mirrored effect and also diffract light similar to a cd?, ""not reflection".
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  7. #6  
    Cool Dude ostkef's Avatar
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    Here's an interesting phenomenon.

    Why is it that a rainbow looks the same when you change your viewing angle?
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  8. #7  
    Genius Duck Dywyddyr's Avatar
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    Quote Originally Posted by theorist View Post
    I thank you , but I still do not think you understand my question, I will re-word it
    Incorrect.
    YOU don't understand your question.

    A cd diffracts light, so would a wet surface have mirrored effect and also diffract light similar to a cd?, ""not reflection".
    Diffraction ONLY occurs when light goes THROUGH the medium.
    As PhDemon has pointed out, this can't happen on a wet road: because the light cannot come UP out of the the puddle.

    Go away.
    Look up the terms you're (mis)using.
    And then think about what you've read.
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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  9. #8  
    Genius Duck Dywyddyr's Avatar
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    Quote Originally Posted by ostkef View Post
    Here's an interesting phenomenon.

    Why is it that a rainbow looks the same when you change your viewing angle?
    Little angels move it round so you stay happy watching the pretty colours.
    Because god loves you and wants YOU to be happy.

    Edit:
    PS I'm not particulary sorry for adding "funny"1 comments. It's a theorist thread - meaning it'll end up in Trash before too long anyway.

    1 I have no idea why I put the word funny in quotes. If anyone didn't think it was funny I suggest they see a good psychiatrist and get themself fixed. I know what funny is, and that was an example.
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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  10. #9  
    Cool Dude ostkef's Avatar
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    Rainbows are quite hard to study because they don't come about very often.

    Of course, one could always make an indoor rainbow with a sprinkler.
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  11. #10  
    Cool Dude ostkef's Avatar
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by ostkef View Post
    Here's an interesting phenomenon.

    Why is it that a rainbow looks the same when you change your viewing angle?
    Little angels move it round so you stay happy watching the pretty colours.
    Because god loves you and wants YOU to be happy.
    I feel so blessed.
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  12. #11  
    Cool Dude ostkef's Avatar
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    Quote Originally Posted by PhDemon View Post
    Or it could be this, take your pick
    Huh?
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  13. #12  
    Cool Dude ostkef's Avatar
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    Quote Originally Posted by PhDemon View Post
    Quote Originally Posted by ostkef View Post
    Rainbows are quite hard to study because they don't come about very often.

    Of course, one could always make an indoor rainbow with a sprinkler.
    They don't need to be studied, this is VERY basic physics and is VERY well understood (by scientists at least - not so much others evidently).

    of course it is. but what if i wanted to demonstrate it? Open a bag of Skittles?
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  14. #13  
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    Quote Originally Posted by PhDemon View Post
    diffraction, refraction and reflection are all different, you seem to use all three terms interchangeably, you need to learn what each is and why they are different. Until you do this you will not understand. Look up each term on Wikipedia and try to figure out what is happening in each case.

    I refer to this quote - Diffraction refers to various phenomena which occur when a wave encounters an obstacle. In classical physics, the diffraction phenomenon is described as the apparent bending of waves.

    And also this quote -Refraction is the change in direction of a wave due to a change in its medium

    I thank you for your patience, the word is diffraction, will a wet surface have a diffraction grating?.

    Question - Is the water on the surface not a different medium?



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  15. #14  
    Genius Duck Dywyddyr's Avatar
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    Quote Originally Posted by theorist View Post
    I thank you for your patience, the word is diffraction, will a wet surface have a diffraction grating?.
    Here we go...

    Quote Originally Posted by Dywyddyr View Post
    Diffraction ONLY occurs when light goes THROUGH the medium.
    To be diffracted light has to come THROUGH the medium from the side opposite where you are looking at it.
    Light does not come UP out of a puddle.
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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  16. #15  
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    Quote Originally Posted by PhDemon View Post
    Reply to post #19

    Well I'd just levitate a droplet in either an electrodynamic balance or optical tweezers system and shine a light at it but thenI have access to a laser lab...

    If you don't try this:

    http://eo.ucar.edu/rainbows/rainbow_ex.html
    I thank you for answering my questions in full. I have saved all links.
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  17. #16  
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by theorist View Post
    I thank you for your patience, the word is diffraction, will a wet surface have a diffraction grating?.
    Here we go...

    Quote Originally Posted by Dywyddyr View Post
    Diffraction ONLY occurs when light goes THROUGH the medium.
    To be diffracted light has to come THROUGH the medium from the side opposite where you are looking at it.
    Light does not come UP out of a puddle.
    I thank you for your answers

    Question - You say light doe's not come up through puddles, so the puddle absorbs all the light or some is still reflected?
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  18. #17  
    Genius Duck Dywyddyr's Avatar
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    If none was reflected you wouldn't be able to see the puddle.
    You're trolling (again).
    We have an entire thread devoted to educating you that things are visible BECAUSE they reflect light into your eyes.
    You were suspended specifically for posting nonsense in that same thread.
    Are you now returned and STILL disputing that particular fact?
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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  19. #18  
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    Quote Originally Posted by Dywyddyr View Post
    If none was reflected you wouldn't be able to see the puddle.
    You're trolling (again).
    We have an entire thread devoted to educating you that things are visible BECAUSE they reflect light into your eyes.
    You were suspended specifically for posting nonsense in that same thread.
    Are you now returned and STILL disputing that particular fact?
    Absolutely nothing to do with the other thread, I am talking about rainbows.

    I will re-word the question, and notice I only have questions with question marks, no suppositions.

    I am starting simple, the rainbow.

    Question - Water reflects light, "so we can see it", a thin surface layer of water will still reflect light. What happens to the light, that travels through our thin layer of water on the surface layer, that "impacts the actual surface", is this all absorbed or would some of the light also reflect?.
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  20. #19  
    Genius Duck Dywyddyr's Avatar
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    Quote Originally Posted by theorist View Post
    Absolutely nothing to do with the other thread, I am talking about rainbows.
    Principles apply regardless of it being rainbows, unicorns or frogs. We see by reflected light.

    Question - Water reflects light, "so we can see it", a thin surface layer of water will still reflect light. What happens to the light, that travels through our thin layer of water on the surface layer, that "impacts the actual surface", is this all absorbed or would some of the light also reflect?.
    If by "actual surface" you mean the surface the water is laying on then yes, some light may/ could/ will be reflected - assuming clear water, and a good viewing angle.
    Now you're going to ask "why isn't that reflected light diffracted?" or "can that reflected light be diffracted?"
    Presumably by waves on the surface of the water.

    IF you had actually read AND understood the Wiki page on diffraction you would also know that diffraction occurs when the "diffraction grating" is of a size that is close to the wavelength of the light. In other words very small gaps. VERY small gaps. REALLY VERY small gaps.
    That isn't going occur in a puddle. I doubt, although I'm open to correction, that it's physically possible for waves in/ on water to form any "grating" small enough to cause visibly discernible diffraction .


    And yes, I hold my hand up over the "light doesn't come up through puddles". I stated that for a number of reasons.
    1) you mentioned on a road - generally puddle water isn't clear enough.
    2) regardless of whether or not light does come up, you don't get diffraction (of light anyway) from water waves. It was (I thought) quicker and easier to stomp before you got all worked up.
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
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  21. #20  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by theorist View Post
    Question - Water reflects light, "so we can see it", a thin surface layer of water will still reflect light. What happens to the light, that travels through our thin layer of water on the surface layer, that "impacts the actual surface", is this all absorbed or would some of the light also reflect?.
    Although you have already shown you are totally dishonest and not here to learn, I still try and help you learn (for some reason).

    • Some light will be reflected from the surface (the amount reflected depends on things like: the angle between the light-surface, the material the light is coming from, etc).
    • Some will pass into the water. The angle of this light will be changed by refraction (depending on the two materials, etc)
    • Some of the light will be absorbed by the water (it is not perfectly transparent).
    • Some of the light will be scattered by impurities in the water.
    • Some will be reflected from the far side of the water (the amount reflected depends on things like: the angle between the light-surface, the material on the other side of the interface, etc).
    • Some will pass through the surface into whatever material is there (the amount will depend on .... well, you get the picture).


    Based on hundreds of years of research, observation and experiment by hundreds of extremely intelligent scientists, all of these factors are very well understood, with detailed theoretical underpinnings that can be used to calculate and predict the effects to high levels of accuracy.

    Why you think anyone should take your vague, incoherent and rambling "thoughts" seriously is beyond me.
    Last edited by Strange; April 11th, 2013 at 06:01 AM. Reason: a bit more detail
    ei incumbit probatio qui dicit, non qui negat
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  22. #21  
    Cool Dude ostkef's Avatar
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    This "theorist" guy sounds very familiar. Very similar to a guy on some other forum who demonstrated a complete lack of understanding of a most basic physics scenario.

    And also appearing to have short term memory loss/ dementia, an complete lack of inability to learn.
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  23. #22  
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    I thank you all for the answers,
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