Question

[Use the fact that surface area of a spherical cap of height $h$ and radius of curvature $r$ is $2πrh$]

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Correct option is C)

$⇒μ1 =sinβ=4/31 $

$⇒sinβ=43 $

$⇒cosβ=47 $

We know

Solid angle, $dΩ=2πR_{2}(1−cosβ)$

Percentage of light $=4πR_{2}2πR_{2}(1−cosβ) ×100$

$=21−cosβ ×100=(84−7 )×100$

$=17% $

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