A mirror faces a cliff located some distance away. Mounted on the cliff is a second mirror,

Question:

A mirror faces a cliff located some distance away. Mounted on the cliff is a second mirror, directly opposite the first mirror and facing toward it. A gun is fired very close to the first mirror. The speed of sound is 343 m/s. How many times does the flash of the gunshot travel the roundtrip distance between the mirrors before the echo of the gunshot is heard?