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## Homework Statement

A car is driven at 30m/s between two sources, each producing sound waves of 1.50x10^6 Hz. The sound heard by driver rises and fades as he travels from one sound source to the other. Find the period of regular fading.

## Homework Equations

No relevant equations provided.

## The Attempt at a Solution

Since the sound rise and fades along the line connecting the two sources, I believe a standing wave has been formed, where the two end points are open ends. I figure that in one second, the car moves 30m and the waves make 1.50x10^6 cycles, so the wavelength (which is the distance covered in one cycle) must equal 2x10^-5 m (or λ=v/f). Since fading takes place at every node, that is λ/2, distance between adjacent nodes = 0.00001 m. how do I translate

that into time interval between successive nodes? The answer given is 3.3 seconds.