A UFO is moving at a constant velocity from along ray , and is horizontal, as shown in the picture. Alice is observing it at point , and , which can be considered constant during the observation.
Given that the UFO is giving off a small pulse of sound wave and then a big pulse after seconds.
If , and the speed of sound in the air is , at what condition for can Alice record the big pulse first and then the small pulse of sound wave?
Take , and the condition is . Submit .