What does the ECM do when it sends radar energy back?

The role of an ECM (Electronic Countermeasures) system is fundamentally about disrupting or confusing enemy radar systems. When the ECM sends radar energy back, it does so in a way that alters the reflections and signals the enemy systems are tracking. This can involve techniques such as jamming signals or creating false targets, making it difficult for the enemy to accurately identify and target the actual aircraft. By confusing the radar systems, the ECM enhances the chances of evading detection and target acquisition, ultimately contributing to the survivability of the aircraft.

As for the other choices, increasing its own detection range does not accurately capture the essence of ECM operations, as ECM is primarily designed to protect rather than enhance your own detection capabilities. Lowering altitude to evade detection is a tactical maneuver unrelated to the electronic countermeasure work of the ECM, and generating electronic noise may be a subset of ECM functions but does not fully describe the primary objective of confusing enemy radar systems.