Question

Two loudspeakers are 25.0 cm apart and produce sound waves in phase. A point on the second nodal line is1.12 m from one source and 2.12 m from the other. What is the wavelength of the waves?

Answer 1

$$\Delta=l_2-l_1=2.12\:\rm m-1.12 \: m=1.0\:\rm m$$

$$\Delta=k\lambda$$

$$\lambda=\frac{\Delta}{k}=\frac{1.0\:\rm m}{2}=0.5\:\rm m=50\: cm$$