Final answer:
The negative wave on an ECG following the P-wave is the Q-wave, which is part of the QRS complex that represents ventricular depolarization.
Step-by-step explanation:
The downward or negative wave of an electrocardiogram (ECG) following the P-wave is the Q-wave. The Q-wave is part of the QRS complex, which represents the depolarization of the ventricles as they pump blood to the lungs and body. The P wave precedes the QRS complex and represents depolarization of the atria, followed by atrial contraction. Immediately after the QRS complex, the T wave signifies ventricular repolarization. Notably, the repolarization of the atria takes place during the QRS complex but is not visible on the ECG as it is overshadowed by ventricular depolarization.