Everyone on the road wouldn't notice that the noise from the siren of an ambulance changes as the ambulance comes closer to us. Did someone notice that while walking or standing on the road? Many would have but nobody would have bothered to check out the concept behind it. It's all because of the Doppler effect of the sound waves. Many teens would have learned about this in high school but nobody would have applied it in real life or bothered to check out its applications. Come on, folks. Let's ponder on the topic 'Applications of Doppler effect'.
Doppler effect is the change in the frequencies of the sound waves when the source travels or the observer travels or even when both travel. I know it's too scientific in nature. Let me try to explain it with an example. You are creating water waves in a ripple tank.
The waves are moving with the same wavelength and frequency. Now you are moving the object that is producing the wave forward with a steady velocity. What do you notice? Do you see the waves are closer in the direction where you were moving the object and the waves are far apart in the opposite direction? This is the Doppler effect. This change in the wavelength and frequency causes the change in sound. Anyways, this Doppler effect not only happens in sound waves. It can happen in any sort of wave which can propagate. Here's an animation to show the Doppler effect. https://en.m.wikipedia.org/wiki/File:Dopplerfrequenz.gif
Here are a few applications of the Doppler effect. Light is used to measure the movement and speed of stars and galaxies. It is also known as the redshift of visible light. Doppler effect is actually used in radars to measure the speed of detected objects. Example: speedometer. Doppler effect is used in robotics. Echocardiogram also uses the Doppler effect to measure the velocity of blood. Instruments such as laser Doppler velocimeter and acoustic Doppler velocimeter uses the Doppler effect to measure the flow of fluids. Satellite navigation and satellite communication are only possible because of the Doppler effect by measuring the shift in the wavelength of EM waves.
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