A C-130 Hercules is traveling toward a cliff

Mission highlight

A C-130 Hercules is traveling toward a cliff at the speed of 150 m/s. Its engines emit a tone at frequency f0. We consider that the speed of sound is 340 m/s. What frequency is received by a pilot after reflection from the cliff?

Image Source: U.S. Air Force
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Why are wet things darker?


When something gets wet, it usually appears darker. Why?
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Disappearing Light

PrismA ray of light is incident on the face AB of a prism at a small angle to the normal and emerges through the face BC. The incident angle is slowly reduced. If the ray of light strikes AB normally then no light emerges through BC at all. This is the initial position so that no light emerges through BC. The angle ABC is 400. What is the refractive index of the material of the prism?


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