Which raypath is known for having the longest detection ranges?

The raypath that is known for having the longest detection ranges is the isothermal raypath. This configuration occurs when the sound speed in the water is uniform or constant with depth, creating a situation where sound waves can propagate efficiently without significant refraction or distortion.

In isothermal conditions, sound travels in straight lines, and the energy of the sound waves is not scattered as much as it would be in a layered or refracted medium. This uniformity allows for minimal loss of signal strength over long distances, enabling detections of acoustic signals over extensive ranges. The lack of layers and the consistency in temperature prevent complex interactions that could otherwise limit the range of detection.

In contrast, options like layered or refracted raypaths involve variations in sound speed due to changes in temperature, salinity, or pressure, which can result in bending or scattering of sound waves, thereby reducing detection ranges. Bottom bounce can also be effective for certain ranges and environments, but typically does not surpass the straight-line propagation of sound in isothermal conditions. Therefore, the isothermal raypath is the most efficient for long-range acoustic detection.