Q. 205.0( 5 Votes )

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Answer :

Given: -

Height of the jar is h,

Transparent liquid of refractive index μ,

There is a dot at the center of bottom surface of the jar.

The problem involves the phenomenon of Total Internal Reflection,

Formula: -

From the required condition for TIR we know that,

Sin i≥μ,


i is the incident angle,

μ is the refractive index of the medium

So, from geometry we can write as,

Where, h is the height of the jar,

R is the radius of the disc,

i is the incident angle,


Using the above expressions, we can write,

R2≥μ2 R22 h2

R2 (1-μ2 )≥μ2 h2

Conclusion: -

The minimum radius of the Disc is,

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