A cylindrical tank is 50.0 ft deep,37.5 ft in diameter,and filled to the top with water.A flashlight shines into the tank from above.What minimum angle φ can its beam make with the water surface if the beam is to illuminate part of the bottom? (nwater = 1.33)

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Quizplus · Accepted Answer

The critical angle for total internal reflection at the water-air interface is given by θc = arcsin(1/nwater) = arcsin(1/1.33) ≈ 48.75°. For the light to reach the bottom, it must refract into the water, so φ must be less than the critical angle. Using Snell's Law and geometry, the minimum angle φ is calculated to be approximately 37.1°.

A Cylindrical Tank Is 50