A diver,below the surface of a lake,notices that no light appears to be coming toward her greater than the angle $\theta$,measured from the vertical.If the index of refraction of water is 1.33,what is the angle $\theta$?
A) 30$^{\circ}$
B) 34$^{\circ}$
C) 37$^{\circ}$
D) 49$^{\circ}$
E) 54$^{\circ}$

Question

Quizplus · Accepted Answer

The angle $\theta$ is the critical angle for total internal reflection. Using Snell's law, $\sin(\theta) = \frac{1}{n}$, where $n$ is the index of refraction of water (1.33). Solving gives $\theta \approx 48.75^\circ$, which rounds to 49°.

A Diver,below the Surface of a Lake,notices That No Light θ\thetaθ

A Diver,below the Surface of a Lake,notices That No Light $\theta$