Final answer:
The nurse should examine the P wave on an ECG strip to observe for atrial depolarization, which is represented by this portion of the ECG and is distinct from the QRS complex and T wave.
Step-by-step explanation:
A nurse examining an ECG strip to observe for atrial depolarization should look at the P wave. The P wave represents this specific electrical activity in the heart, indicating that the atria are contracting and pumping blood into the ventricles. It is distinct from the QRS complex, which signifies ventricular depolarization, and the T wave, which represents ventricular repolarization.
Atrial repolarization occurs during the QRS complex but is masked by the stronger electrical activity of the ventricles, so it is not visible on the ECG.