An airplane traveling at one third the speed of sound (i. e., 114 m/s) emits a sound of
frequency 3.76 kHz.
At what frequency does a stationary listener hear the sound as the plane approaches?
Answer in units of kHz.

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as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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