CBSE Class 11-science Answered

Dear Student

Depth of fish below water  h=12 cm
radius of the view         = r
Refractive index of water n=3/4

For total internal reflection to takeplace
n=sin (theta)=3/4
h,r are sides of a right angle triangle.
where the theta id the angle between hypotenues and h of teh triangle.

tan (theta)=r/h
sin(theta)/cos(theta)=r/h;

cos (theta)= sqrt(1-sin^2(theta))= sqrt(1-9/16)=sqrt(7/9);

r=h sin(theta)/cos(theta)=12X (3/4)/sqrt(7/9)=9sqrt(7/9)=7.938 cm

REgrds
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