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Homework Help: Refraction at a spherical surface

  1. Aug 14, 2009 #1
    1. The problem statement, all variables and given/known data


    2. Relevant equations

    3. The attempt at a solution

    I was kind of confuse with the use of refractive index.

    For the first part of question, n1 = 1.00 and n2 = 1.50. From what I know, the object is at vacuum so the n1 = 1.00.

    But why for the second part of the question, n1 = 1.50 and n2 = 1.00 ? After the first refracting surface, the image should be at the vacuum too. But why we use n1 = 1.50?

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  2. jcsd
  3. Aug 14, 2009 #2


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    Welcome to PF!

    Hi stpmmaths! Welcome to PF! :smile:
    (I can't see your attachment yet, but …)

    I assume that the light starts by going into the sphere from the air (or vacuum), so it's going from n = 1 to n = 1.5;

    then it travels through the sphere (n = 1.5) until it hits the opposite surface and comes out again, so it's going from n = 1.5 to n = 1. :wink:
  4. Aug 14, 2009 #3
    Ok..I understand a bit.

    Now I came across with another question similar to this question(quite similar)

    Quenstion: attachment.php?attachmentid=20113&stc=1&d=1250304700.jpg

    Why the n1 is 1.50 if we say the light starts from vacuum?:confused:

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  5. Aug 15, 2009 #4


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    Because the light starts from the coin, inside the sphere, not from vacuum. :wink:
  6. Aug 15, 2009 #5


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    Look carefully at the arrows in the figure. Where do they start from?

    EDIT: to clarify, look at the interface where the two rays meet. The ray arrows indicate they go from the glass into the air.

    p.s. Hello tiny-tim!
  7. Aug 15, 2009 #6
    Oo, I got it.
    Thanks everyone.
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