Dr. Doppler is a physicist known for his work in the field of wave phenomena. He is best recognized for the Doppler Effect, which describes the change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave. This principle is commonly observed in sound waves, such as the changing pitch of a passing siren. Born in 1803 in Austria, Dr. Doppler's research extended beyond sound to include light waves. His findings have significant applications in various fields, including astronomy, where it helps in measuring the speed of stars and galaxies, and in medical imaging, particularly in ultrasound technology.