Which instrument is used to study undulations in arterial pressure?

The kymograph is the correct instrument used to study undulations in arterial pressure. This device records changes in pressure and waveforms over time, capturing continuous variations in arterial pressure that can be analyzed for clinical assessments.

Kymographs are particularly effective in this context because they provide a visual representation of pressure changes, allowing for detailed analysis of the rhythmic oscillations associated with the heartbeat and vascular health. This is crucial for understanding conditions related to blood pressure, circulation, and overall cardiovascular function.

Other instruments listed serve different purposes. A laparoscope is primarily used in minimally invasive surgical procedures for viewing inside the abdomen, whereas a photometer measures light intensity, and a stethoscope is designed for listening to the internal sounds of a patient's body, such as heartbeats and breath sounds. While a stethoscope can provide some information on cardiovascular health, it does not record arterial pressure undulations in the same detailed manner as a kymograph does.