Assertion (A): Critical angle of light passing from glass to air is minimum for violet colour.

  Reason (R) : The wavelength of blue light is greater than the wave length of other colours

When light ray is passing from glass to air

we get $\sin \hspace{0.17em}\mathrm{C}=\frac{1}{{\mathrm{\mu }}_{\mathrm{g}}} \mathrm{but} \mathrm{\mu }\propto \frac{1}{\mathrm{\lambda }}$

Since wave length of violet $\left({\mathrm{\lambda }}_{\mathrm{v}}\right)$is minimum so ${\mathrm{\mu }}_{\mathrm{v}}$is maximum

$\Rightarrow$We get sin C for violet also minimum hence critical angle of violet is minimum assertion is

true

But in Reason : it is given ${\lambda }_B$is greater than other colours it is false because

${\mathrm{\lambda }}_{\mathrm{B}}<{\mathrm{\lambda }}_{\mathrm{g}}<{\mathrm{\lambda }}_{\mathrm{y}}<{\mathrm{\lambda }}_{\mathrm{O}}<{\mathrm{\lambda }}_{\mathrm{R}}$in (VIBGYOR)