If your radar indicates a target, but there is no visible object at the point indicated, what should you suspect if a large mountain is breaking the horizon on the same bearing?

In the context of radar operation and the scenario described, ducting is the correct concept to understand. Ducting refers to a phenomenon where radar waves travel over the horizon due to temperature inversions or other atmospheric conditions that cause the radar signal to be refracted back towards the ground. In this situation, if the radar indicates a target along the same bearing where a large mountain is present, it suggests that the radar signals are being bent due to the atmospheric conditions created by the mountain's geographical influence.

This phenomenon could lead to the radar detecting a target that is not actually present at the indicated position, especially if the radar beam is inadvertently reflecting off the mountain's surface or other features in the vicinity. Understanding ducting is crucial for radar operators because it can lead to misinterpretations of radar data, particularly in mountainous areas where line of sight may be compromised by terrain.

In contrast, the other choices do not directly relate to this specific situation. Sub-refraction typically results in radar signals not reaching targets due to insufficient bending of the radar waves, which would not likely result in the target indication the operator is experiencing. Ionospheric skip waves are more relevant to long-range radio communications rather than radar detection, and a submerged submarine, while a conceivable