Question

With respect to air critical angle in a medium for light of red colour $\left[{\lambda }_1\right]is\theta .$ Other facts remaining same,critical angle for light of yellow colour $\left[{\lambda }_2\right]$ will be

• A. $\theta$
• B. $Morethan\theta$
• C. $lessthan\theta$
• D. $\frac{{\theta \lambda }_1}{{\lambda }_2}$

Answer 1

Answer: (C)

$lessthan\theta$

Critical angle $=si{n}^{-1}\left(\frac{1}{\mu }\right)$
$\therefore \theta =si{n}^{-1}\left(\frac{1}{{\mu }_{{\lambda }_1}}\right)and{\theta }^{\prime }=si{n}^{-1}\left(\frac{1}{{\mu }_{{\lambda }_2}}\right)$
Since ${\mu }_{{\lambda }_2}>{\mu }_{{\lambda }_1}$, hence ${\theta }^{\prime }<\theta$