Doppler effect

A police speed check operates by reflecting radio waves of frequency 100MHz from passing cars. It is found that the frequency after reception has decreased by 18Hz.

What is the frequency change if the radar speed detector is placed in front of an approaching car?

What is the advantage of placing the detector behind the car instead of in front?

Update:

Plz calculate the frequency change.

1 Answer

Rating
  • 天同
    Lv 7
    1 decade ago
    Favorite Answer

    What is the frequency change if the radar speed detector is placed in front of an approaching car?

    The frequency will be increased instead of decrease.

    What is the advantage of placing the detector behind the car instead of in front?

    Driver would notice the presence of the radar and they would slow down accordingly.

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