I'm looking at this problem and I need help with it. By the way the ones who helped me on my last few questions... thanks! I did well on my exam thanks to you!
Problem:
A lamp is located 1 meter below the surface of a lake. Calculate the diameter of the area at the surface which is illuminated lamp, when viewed from above the surface. The refractive index of water is 1.33.
Help!
2007-03-28 17:29:17 · 1 answers · asked by Sir Guitarist 2 in Science & Mathematics ➔ Physics
The key to this problem is to determine the angle at which there is total internal reflection. This angle is called the Brewster angle. recall Snell's law
n1sinx1=n2sinx2
1.33sinx1=1sin90
x1=arcsin(1/1.33)=48.75
Consider a triangle starting at the light with the hypotenuse going to the surface at an angle versus the verticle of 48.75. The leg of the right triangle is 1 m. therefore the length of the other leg is (using the law of sines)
sin48.75/sin41.25*1=1.14 m. Make this the radius therefore
the area illuminated is pi*r^2=pi*(1.14)^2=4.08 m^2
2007-03-28 18:13:55 · answer #1 · answered by Rob M 4 · 0⤊ 0⤋