1. New SDN Article! Q&A with Dr. Sarah Lawrence, Pharmacist and Educator
    Dismiss Notice
  2. Download free Tapatalk for iPhone or Tapatalk for Android for your phone and follow the SDN forums with push notifications.
    Dismiss Notice
Article: Sarah Lawrence Tapatalk
Dismiss Notice
Visit Interview Feedback to view and submit interview information.

Total internal reflection question

Discussion in 'MCAT Study Question Q&A' started by dorjiako, Aug 18, 2011.

Previous Thread Next Thread
Loading...
  1. dorjiako

    dorjiako
    2+ Year Member

    Joined:
    Dec 9, 2010
    Messages:
    71
    Likes Received:
    0
    The question says: Light from air strikes a translucent plastic material. If the light strikes at an angle of 30 degrees to the material and bends by 15 degress, what is the index of refraction of the plastic?

    Looks pretty easy on the surface but is unable to get their answer 1.22. Any input on how they arrived at their answer is highly welcomed.
     
    #1 dorjiako, Aug 18, 2011
    2. Note: SDN Members do not see this ad.

  2. tmh

    tmh

    Joined:
    Jul 2, 2011
    Messages:
    104
    Likes Received:
    0
    Status:
    Pre-Medical
    This is sort of weirdly written, but I got the answer.

    First, if light is entering at 30 degrees to the material, it's 60 degrees to the normal. When it says it bends by 15 degrees, I think it means that the angle of refraction is 15 degrees smaller (45 degrees).

    So 1.00sin60 = nsin45
    n = 1.22
     
    #2 tmh, Aug 18, 2011
  3. FutureDoctor503

    FutureDoctor503 A.W.E.S.O.M.-O
    5+ Year Member

    Joined:
    Apr 13, 2011
    Messages:
    109
    Likes Received:
    0
    Status:
    Pre-Medical
    n1*sin theta1 = n2*sin theta2
    n1 = 1
    sin theta1 = 60 degrees because the questions says light strikes at an angle of 30 degrees to the material (in the equation, we have to use the angle from the normal (90-30=60)
    sin theta2 = 45 degrees because the question says the light bends by 15 degrees (60-15=45 degrees from the normal)
    If you plug in these numbers, you should be able to get the answer. :)
     
    #3 FutureDoctor503, Aug 18, 2011
  4. dorjiako

    dorjiako
    2+ Year Member

    Joined:
    Dec 9, 2010
    Messages:
    71
    Likes Received:
    0
    Thanks again. I was using n1sin 60degree = n2 sin 15 degrees (instead of substracting 15 from 60). Thanks again.
     
    #4 dorjiako, Aug 18, 2011
  5. tmh

    tmh

    Joined:
    Jul 2, 2011
    Messages:
    104
    Likes Received:
    0
    Status:
    Pre-Medical
    Also, this is not total internal reflection.
     
    #5 tmh, Aug 18, 2011
  6. dorjiako

    dorjiako
    2+ Year Member

    Joined:
    Dec 9, 2010
    Messages:
    71
    Likes Received:
    0
    You are right. However, this problem was asked under Kaplan's mcat high yield total internal reflection section. It was probably while I was tring to figure out how internal reflection applied to the question as I tried to solve it.
     
    #6 dorjiako, Aug 18, 2011
Previous Thread Next Thread
Loading...
(You must log in or sign up to post here.)

Share This Page