What is the name of the phenomenon where a moving source of sound causes an apparent shift in frequency for a stationary observer?

💡 Solution & Explanation

The Doppler effect describes the apparent change in the frequency or pitch of a sound wave perceived by an observer when the sound source or the observer is in motion relative to each other. The photoelectric effect explains the emission of electrons from metal surfaces when illuminated by light of adequate frequency, demonstrating the particle nature of light. The Doppler effect has diverse practical applications ranging from astronomical red-shift measurements to medical ultrasound imaging.