Solved: PHYSICS Question for NEET

NEET PHYSICSMedium

A ray of light traveling in a transparent medium of refractive index $\mu$ falls on a surface separating the medium from the air at an angle of incidence of $45^{\circ}$ . For which of the following values of $\mu$ can the ray undergo total internal reflection?

$\mu=1.33$

$\mu=1.40$

$\mu=1.50$

$\mu=1.25$

Step-by-Step Solution

Condition for Total Internal Reflection (TIR): For TIR to occur, the angle of incidence ( $i$ ) must be strictly greater than the critical angle ( $i_c$ ). That is, $i > i_c$ , which implies $\sin i > \sin i_c$ .
Critical Angle Formula: The sine of the critical angle is given by the ratio of the refractive index of the rarer medium to the denser medium: $\sin i_c = \frac{\mu_{air}}{\mu_{medium}} = \frac{1}{\mu}$ .
Calculation: Given that the angle of incidence $i = 45^{\circ}$ , we have: $\sin(45^{\circ}) > \frac{1}{\mu}$ $\frac{1}{\sqrt{2}} > \frac{1}{\mu}$ $\mu > \sqrt{2}$ $\mu > 1.414$
Conclusion: Among the given options, only $\mu = 1.50$ satisfies the condition $\mu > 1.414$ .

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