A sound wave traveling downward with a speed of about 4,000 m/s suddenly slows to 1,500 m/s not far below the Earth’s surface. What has the sound wave most likely encountered? (Its B) A. a different kind of rock B. an underground lake C. an open cavity D. a pile of dinosaur bones

The correct answer is B. An underground lake

Explanation:

Sound moves more slowly in liquids or gases than in solids, in which particles are together. Additionally, the speed of sound is measured in meters per second or m/s. In this context, if the speed of a sound wave reduced from 4,000 m/s to 1,500 m/s while traveling through the surface of Earth, which is solid, it is likely the cause is a change in the medium the wave is going through.

Moreover, the average speed of sound in air is below 400 m/s, this suggests the sound was not traveling through an open cavity. However, the speed in liquids such as water is around 1480 m/s, this is quite similar to the second speed registered. According to this, the sound wave slowed because it was traveling through a liquid medium; therefore, the answer is an underground lake.

UNDERGROUND LAKE

Explanation: