Who is the Austrian physicist known for the discovery that relative motion causes frequency change?

The Austrian physicist recognized for the discovery that relative motion leads to a change in frequency, known as the Doppler effect, is indeed Christian Johann Doppler. This phenomenon describes how the frequency of waves (such as sound or light) varies for an observer moving relative to the source of the waves. When the source of waves moves closer to an observer, the waves are compressed, leading to a higher frequency (or pitch in sound), while if the source moves away, the waves are stretched, resulting in a lower frequency.

Doppler's work was groundbreaking in its application to various fields, such as astronomy and radar technology, and has profound implications in understanding wave behavior in different contexts. His findings laid the groundwork for subsequent developments in physics and engineering, influencing areas like sound localization and the motion of celestial bodies.