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A point source of light is placed at a d...

A point source of light is placed at a distance `h`below the surface of a large deep late.What is the percentage of light energy that escapes directly form the water surface is `mu`of the water=`4//3`?(neglet partial reflection)

A

`50%`

B

`25%`

C

`20%`

D

`17%`

Text Solution

Verified by Experts

The correct Answer is:
D
Soild image `(phi)=2pi(1-cos theta)`
`"where" theta ="plane angle"`

`"escape energy" =("total energy")/(4pi)xx"solid angle"`
`"escaped energy"/"total energy"=1/(4pi)xx2pi(1-cosC)`
`=1/2(1-cosC)`
form law of refraction
`mu_w sin i= mu_a sinr`
`4/3xxsin C=1xxsin90^@`
`sin C=3/4 implies cos C=sqrt(1-sin^2C) implies cos C=sqrt7/4`…(2)
from(1)and(2)
`("escaped energy")/("total energy")=(1)/(2)(1-(sqrt(7))/(4))`
`("escaped energy")/("total energy")=0.17`
`"total" % "escape" "enscaped" =17%`
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