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Finding angle of refraction given angle of incidence?

  • #1
Can someone help me in solving this question ?

my attemp is sin42/sin 90 to get the refractive index then n =sin i/sin r to get c
and for b n=1/sinc
Physics.jpg
 

Answers and Replies

  • #2
TSny
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Welcome to PF!

Try to answer part (i) first by examining the diagram and using a little geometry.
 
  • #3
Thanks for responding but i am trying but cant figure it out its probably right there in my face but i just cant see it yet
 
  • #4
TSny
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What is the value of the angle DBM shown below?
 

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  • #5
that would be 90 ?
 
  • #6
TSny
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Yes, I think that's what you are supposed to assume. The fisherman's net (at D) is assumed to be essentially at the surface of the water.
 
  • #7
so there fore the angle of incidence is 90 so that means C would be a critical angle
 
  • #8
TSny
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so there fore the angle of incidence is 90 so that means C would be a critical angle
Yes. From the diagram, can you determine the value of the critical angle in degrees?
 
  • #9
42 ? i doubt you can just determine it from looking at the diagram as the question asks to calculate it
 
  • #10
TSny
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Note that the line connecting point A to Nemo's eye is a straight line.
 

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  • #11
therefore c must be 180-(42+90)
 
  • #12
TSny
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Yes
 
  • #13
well it makes sense because the answer is 48 and 48 is the critical angle of air-water boundary so now i find the refractive index 1/48
 
  • #14
TSny
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Why 1/48?
 
  • #15
because there is a formular which says that N(Refractive index) = 1/ sin C(48) oh i see yeah im suppose to sin the 48
 
  • #16
TSny
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Yes, good.
 
  • #17
thank you very much
 

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