Physics Help Forum Reflection Problem When Diving

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 Nov 23rd 2010, 07:43 AM #1 Junior Member   Join Date: Oct 2010 Posts: 28 Reflection Problem When Diving "At what angle to the surface must a submerged diver in a lake look toward the surface to see the setting sun just along the horizon?" So once the angle of incidence hits the water, it gets refracted down forming a smaller angle than the angle of incidence. But is there a formula you can use to find the actual angle that the diver must look at to see the sun?
 Nov 24th 2010, 11:28 PM #2 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 Use: (sin i)/(sin r) = 1.33 where i is the incident angle, r is the refracted angle that you are looking for 1.33 is the refractive index of water. I assume that there is no total internal reflection involved... and that the sun is taken to be at 90 degrees. __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?
Nov 27th 2010, 06:33 PM   #3
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 Originally Posted by Unknown008 Use: (sin i)/(sin r) = 1.33 where i is the incident angle, r is the refracted angle that you are looking for 1.33 is the refractive index of water. I assume that there is no total internal reflection involved... and that the sun is taken to be at 90 degrees.
Okay so then to do the math for this problem it would be

Sin i/sin r = 1.33
sin 90 = 1.33 sin r
sin 90/1.33= sin r which is .75?

 Nov 28th 2010, 09:56 AM #4 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 Yes, this is the value of sin r. Find r now. __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?
Nov 28th 2010, 10:51 AM   #5
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 Originally Posted by Unknown008 Yes, this is the value of sin r. Find r now.
So then sin .75= .01? So then the angle is .01?

 Nov 28th 2010, 10:57 AM #6 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 No. Have you learned arcsine or sine inverse? If sin (x) = y Then x = sin^(-1) (y) or x = arcsin (y) __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?
Nov 29th 2010, 06:43 AM   #7
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 Originally Posted by Unknown008 No. Have you learned arcsine or sine inverse? If sin (x) = y Then x = sin^(-1) (y) or x = arcsin (y)
Ahh i gotcha, so it would be 48.6 then correct?

 Nov 29th 2010, 07:27 AM #8 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 Yes! That's right! __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?
Feb 9th 2011, 07:27 PM   #9
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 Originally Posted by Unknown008 Yes! That's right!
Could you explain why you assume that the sun is at 90 degrees? Is it 90 degrees to the normal?

 Feb 9th 2011, 10:01 PM #10 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 Yes, because when the sum sets, it's at level ground, hence, at 90 degrees to the normal __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?

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# The refractive index of water is 1.33. A diver in water will see the setting sun, at an angle of

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