Un efecto extremadamente importante para algunas aplicaciones que involucran sonidos y ultrasonidos y ondas electromagnéticas es el "efecto Doppler".

En aras de la explicación, tomemos el sonido como ejemplo, pero lo mismo es cierto para las ondas electromagnéticas, en el caso del radar.

Cuando emitimos un sonido hacia un objeto en movimiento, el movimiento del objeto hace que la onda reflejada cambie en frecuencia, como se muestra en la figura 1.

 


 

 

De una manera simple de entender, podemos decir que, si el objeto se aleja de la fuente emisora, como se muestra en la figura 2, las ondas emitidas se "estiran" y el sonido que regresa tiene una longitud de onda más larga o una frecuencia más baja.

 


 

 

 

Si el objeto se acerca a la fuente emisora, las ondas reflejadas tienen su longitud "reducida" y con esto el sonido que regresa es más alto, es decir, tiene una frecuencia más alta.

Podemos ver esto fácilmente cuando un automóvil a toda velocidad nos toca la bocina. Cuando llega, la bocina suena más aguda que cuando se aleja.

En el momento exacto en que pasa, percibimos la transición del sonido.

Si conocemos la frecuencia del sonido emitido y medimos la frecuencia del sonido que regresa, podemos determinar con precisión la velocidad del objeto en el que se refleja.

Este principio, como puede ver el lector haciendo clic en Radar, también se usa con ondas de radio, donde también se observa el efecto Doppler, para radares que miden la velocidad de los vehículos en las carreteras.

Del libro Curso de Electr[ónica – Electrónica Analógica de Newton C. Braga

 

 

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