A wave of frequency 500 Hz has velocity 360 m/sec. The distance between two nearest points 60° out of phase, is

The distance between two points i.e. path difference between them $\mathrm{\Delta }=\frac{\mathrm{\lambda }}{2\mathrm{\pi }}\times \mathrm{\phi }=\frac{\mathrm{\lambda }}{2\mathrm{\pi }}\times \frac{\mathrm{\pi }}{3}=\frac{\mathrm{\lambda }}{6}=\frac{\mathrm{v}}{6\mathrm{n}}$

$(\because \mathrm{v}=\mathrm{n\lambda })\Rightarrow \mathrm{\Delta }=\frac{360}{6\times 500}=0.12\mathrm{m}=12\mathrm{cm}$