For the refraction of light through a prism

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Angle of minimum deviation will increase if refractive index of prism ( $μ_{P}$ ) is increased keeping the refractive index of the outside medium ( $μ_{S}$ ) unchanged if $μ_{P} > μ_{S}$ .

For every angle of deviation there are two angles of incidences

The light travelling inside an equilateral prism is necessarily parallel to the base when prism is set for minimum deviation

There are two angles of incidence for the deviation, which is other than minimum

answer is B, C, D.

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Detailed Solution

For deviation angle $δ$ to be minimum, we need
i = e
$\begin{array}{l} \Rightarrow r_{1} = r_{2} \\ \Rightarrow r_{1} + r_{2} = A \\ \Rightarrow r_{1} = 30^{0} \end{array}$
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If r₁ = 30^o then ray AB must be parallel to base of prism for minimum deviation so there can be only single angle of deviation but for other deviation angles there can be two angle of incidence ( $θ$ ₁, $θ$ ₃), the figure shows the variation of deviation angle with angle of incidence.
Question Image
In general for small angled prism, we have
$δ = (μ - 1) A$
Where we can see that as increases, also increases.