ray-optics-and-optical-instruments Question 16
Question: Q. 9.5, Page 55]
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Solution:
Ans. Correct option : (c)
Explanation : According to the Cauchy relationship,
$$ \lambda \propto \frac{1}{\mu} $$
Smaller the wavelength higher the refractive index and so that smaller the critical angle
So, light rays are passing from denser to rarer medium. As $\sin C=\frac{1}{\mu}$ so, $C \propto \frac{1}{\mu}>\mu_{v}>\mu_{g}>\mu_{y}>\mu_{R}$
So, critical angle for $C_{v}<C_{g}<C_{Y}<C_{R}$, that is, critical angle of blue and green light is smaller than that of yellow and it is greater for red colour light. As the angle of refraction for yellow light is for a particular incident angle, this incidence angle is critical angle for yellow. Let it be $C_{\gamma}$.
As we know that, $C_{R}>C_{v}$.
So, it will not get total internal reflection and $C_{V}<$ $C_{Y}, C_{G}<C_{Y}$.
So, light of blue and green colour get total internal reflection.
