A sound wave of 40.0 cm wavelength enters the tube shown in the figure at the source end. What must be the smallest radius r of the curved path such that a maximum intensity will be heard at the detector end?

The smallest value of r is cm

Answer

But

If we take the smallest non-zero DL in terms of the wavelength we get

Sound travels through two different paths. The path length difference between the two sound waves is

Since we want a __
maximum sound__ at the detector, the relationship between the path length
difference and the wavelength is

2-4 Interference

Example 2