Home > Encyclopedia of Science > Doppler Effect

• Explanation
• Words to Know
• Doppler effect in light waves
• Applications

The Doppler effect is an effect observed in light and sound waves as they move toward or away from an observer. One simple example of the Doppler effect is the sound of an automobile horn. Picture a person standing on a street corner. A car approaches, blowing its horn. As the car continues moving toward the person, the pitch of the horn appears to increase; its sound goes higher and higher. As the car passes the observer, however, the effect is reversed. The pitch of the car horn becomes lower and lower.

Explanation

All waves can be defined by two related properties: their wavelength and frequency. Wavelength is the distance between two adjacent (next to each other)...