Doppler Effect

Doppler EffectDoppler effect is a change in the length of the electromagnetic wave caused by movement of the source, which is registered by a receiver. It is easy to observe in practice, when a car with a switched on siren passes by. Let's assume the siren produces a certain tone, and it does not change. When the car is not moving towards the observer, then he hears exactly the tone that the siren produces. But if the car is getting closer to the observer, the frequency of the sound waves will increase (and the length will decrease). The tone that the observer will hear will be higher than the one the siren is actually producing. When the car is passing by the observer, he will hear the same tone that siren is actually producing. And when the car will drive by and will be moving away, not getting closer, the observer will hear a lower tone, due to the lower frequency (and thus greater length) of the sound waves.For waves (e.g. sound) disseminating in some medium one has to consider movement of both the source and the wave receiver relative to the environment. For electromagnetic waves (e.g. light) that do not need any environment to disseminate in, only the relative motion of the source and the receiver are important.This effect was first described by Christian Doppler in 1842.This is how you can observe the Doppler effect: As the phenomenon is typical for any oscillatory processes, it is very easy to observe it for the sound. Sound waves frequency is perceived by the ear as a pitch. You need to wait for a fast-moving car or train to pass by with a sound, such as a siren or just a beep. When the car is approaching, you will hear the pitch higher. Then, when the car catches up with you, the pitch will drop sharply and then, when the car is moving away, the siren pitch will be lower.

Category:

Science & Technology

Tags:

• effect
• electromagnetism
• physics
• wave

[scepticulous]

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