Infinite Iterations!!!

A missile was chasing an airplane at a rate of 2000 meters per second. The airplane was fleeing from the torpedo at a speed of 1900 meters per second. Suppose that the torpedo has a unique homing device which emits a radio wave with a speed of 5000 meters per second. Say the radio wave was emitted when the missile was 15000 m away from the airplane. How many meters does the radio wave travel before the missile hits the airplane and blows it up?

Assumptions: The speed of the wave is always constant. As soon as the wave hits one surface, it bounces off in an opposite direction.