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Pyrex glass rod is immersed into wesson oil

  1. Mar 4, 2008 #1
    http://littleshop.physics.colostate.edu/onlineexperiments/Pyrex and Oil.html

    I want to show the math of what happens when the pyrex glass rod is immersed into wesson oil making the bend in light identical, but I don't know where to start? Suggestions? Or equations you believe I should focus on?
  2. jcsd
  3. Mar 5, 2008 #2


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    Have you had Snell's Law yet? If so, consider the angle that a light ray makes to the normal to the surface of the rod both before entering the glass and after, when the index of refraction is the same on both sides of the surface. How does that differ from how the light ray travels in simply passing through the oil?
  4. Mar 5, 2008 #3
    No, but I've googled it and found out the relation that:

    refraction1 * angle1 = refraction2 * angle2

    refraction1 / refraction2 = wave velo.2 / wave velo.1

    thus if the refraction of two things are equal where

    refractoin1 = refraction2

    thus it having both equal each other the thing would equal 1=1 which causes no bend in light..... however this does not explain why it looks to be invisible? for example why are bubbles visible when it itself is a clear object without color? someone please explain...
  5. Mar 5, 2008 #4


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    The rod becomes "invisible" because there is no change in the direction of the light rays passing from the oil to the glass and back out to the oil, just as if there were no rod there at all. (Actually, slight variations in the refraction just at the surface where the oil density is disturbed by the presence of the rod will allow the edges of the rod to be just discernible.)

    The difference with bubbles is that they are not solid objects, but "chambers" filled with air, surrounded by the fluid (water or whatever). So light will be passing from the fluid (with some index of refraction n > 1) to the air within the bubble (n very nearly equal to 1) and back into the fluid. The path of the light ray is disturbed, so you are able to see bubbles.
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