Final answer:
The T wave on the electrocardiogram (ECG) represents ventricular relaxation or diastole when the heart is trying to rest.
Step-by-step explanation:
The wave that represents when the heart is trying to rest is known as the T wave. This wave on the electrocardiogram (ECG) signifies the repolarization of the ventricles, which is an indicator of ventricular relaxation or diastole. During this phase, the heart muscle recovers from the contraction and prepares for the next cycle. It is a critical component of the cardiac cycle and lasts approximately 430 milliseconds. Understanding the T wave and its significance in the ECG can provide insight into the heart's health and function.