A blue-green laser is being tested as an experimental aircraft-to-submerged subm

Question

A blue-green laser is being tested as an experimental aircraft-to-submerged submarine communications system. Given the laser operates at a wavelength of 490 nm and is incident at an angle of 30.0 degrees to the normal to the ocean surface, and if the index of refraction in seawater is 1.33, (a) If the submarine is at a submerged position at an angle of 20 degrees to the normal to the ocean surface and in the same plane with respect to the aircraft, can communications be established knowing the laser beam is very narrow,

Explanation / Answer

a)

from snells law

n1sino1=n2sino2

1*sin30=1.33*sino2

o2=sin-1(sin30/1.33)=22.08o

since the submarine submerged at an angle of 20o to the normal to the ocean surface , but the angle of refracted light is 22o .so he communiation cannot be established .

b) wave length of ligth in sea water is

lambda'=lambda / n2=490/1.33=368.42 nm

c)   speed of light in sea water

v=c/n=(3*108)/1.3= 2.255 *108 m/s

d)   frequency of laser transmitted by air craft

f=c/lambda=(3*108)/(490*10-9)=6.12*1014Hz

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