Physics - Geometrical Optics Question with Solution | TestHub

For $\mathrm{AB}=20\mathrm{cm}$, a narrow parallel beam entering from left side will come out from other side as a parallel beam.

For $\mathrm{AB}=20\mathrm{cm}$, and surrounding air being replaced by a medium, $\mu =3/2$, on both sides, parallel light beam will come out as a diverging beam.

For $\mathrm{AB}=20\mathrm{cm}$, and surrounding air being replaced by a medium, $\mu =3/2$, on both sides, parallel light beam will come out as a parallel beam.

For surrounding $\mu =3/2$, if emergent beam has to be parallel then AB has to be bigger than 20 cm .