Two loudspeakers emit sound waves along the x-axis. The sound has maximum intensity when the speakers are 19 cm apart. The sound intensity decreases as the distance between the speakers is increased, reaching zero at a separation of 29 cm. What is the wavelength of the sound? Express your answer using two significant figures.

The former is the case of constructive interference and the later case relates to destructive interference.

For listener, path difference is the separation of loudspeaker as listener is not standing in between the speaker.

If λ be the wave length

For constructive interference

19 = n λ

For destructive interference

29 = (2n+1) λ / 2

= n λ + λ / 2

= 19 + λ / 2

10 = λ / 2

λ = 20 cm

= 0. 20 m