Question

You are given four sources of light each one providing a light of a single colour - red, blue, green and yellow. Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incidence at the interface of two media is $90^{\circ}$. Which of the following statements is correct, if the source of yellow light is replaced with that of other lights without changing the angle of incidence?

• A. The beam of red light would undergo total internal reflection
• B. The beam of red light would bend towards normal while it gets refracted through the second medium
• C. The beam of blue light would undergo total internal reflection
• D. The beam of green light would bend away from the normal as it gets refracted through the second medium

Answer 1

The Correct Option is C

Here, for yellow light, $r = 90^{\circ}$ when $i = C$. As $i$ is kept same, $C$ must be smaller for total internal reflection. From $\mu =\frac{1}{sin\,C} , C$ will be smallest for blue colour. Therefore, blue light would undergo total internal reflection.