1-A point source of light is located 3.36 m below the surface of a large lake of
ID: 1702146 • Letter: 1
Question
1-A point source of light is located 3.36 m below the surface of a large lake of clear toxic fluid (Lake Ontario, where n=1.44). Find the area of the largest circle on the pool's surface through which light coming directly from the source can emerge.
Correct, computer gets: 3.30E+01 m^2
2-A laser beam enters a 16.5 cm thick glass window at an angle of 65o (from the normal). The index of refraction of the glass is 1.40. At what angle from the normal does the beam travel through the glass? Use units of "deg".
Correct, computer gets: 4.03E+01 deg
3-How long does it take the beam to pass through the plate?
I just don't know how to do the third question, so plz help me
Explanation / Answer
The definition of the index of refraction, n
v = c / n
where v = velocity of light in a medium
c = speed of light in a vacuum, 3.00 x 108 m/s
Given n = 1.40, d = 16.5 cm
t = d / v
t = d / (c/n)
t = [ 16.5 x 10-2 m / (3.00 x 108 m/s / 1.4) ]
t = 7.920 x 10-10 s
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