KVPY 2020-21 SB SX Exam Previous Papers

A right-angle isosceles prism is held on the surface of a liquid composed of miscible solvents $\mathit{A}$ and $\mathit{B}$ of refractive index ${\mathit{n}}_{\mathit{A}}=1.50$ and ${\mathit{n}}_{\mathit{B}}=$1.30, respectively. The refractive index of prism is ${\mathit{n}}_{\mathit{p}}=1.5$ and that of the liquid is given by $\mathit{n}\mathit{L}$ $={\mathit{C}}_{\mathit{A}}{\mathit{n}}_{\mathit{A}}+\left(1-{\mathit{C}}_{\mathit{A}}\right){\mathit{n}}_{\mathit{B}}$, where ${\mathit{C}}_{\mathit{A}}$ is the percentageof solvent $\mathit{A}$ in the liquid :- If ${\mathrm{\theta }}_{\mathit{C}}$ is the critical angle at prism-liquid interface, the plot which best represents the variation of the critical angle with the precentage of solvent is: