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A liquid of refractive index 1.5 is pour...

A liquid of refractive index 1.5 is poured into a cyclindrical jar of radius 20 cm upto a height of 20 cm. A small bulb at the centre of bottom glowing. Find area of the liquid surface through which the light of the bulb passes into air.

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Let S be the small bulb at the bottom ofthe jar. The bulb is in the denser medium. The light from the bulb is incident on the water - air interface. Light emerges for incident angles less than the critical angle. The locus of all the points on the surface of the water that produces an angle of incidence C is a circle of radius r.
In the A DBS, tan C = `r/h` , r=h tan C ,r `h/(sqrt(mu^(2)-1))`
The area of the surface through which the light passes,
A=`pir^(2) = (pixx(0.20)^(2))/(1.5^(2)-1) = 0.1005m^(2)`
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