Radar and Flow

Applied Physics Lab 04

NAME: ___________________________

DATE: ___________________________

1

The Radar Loop

In a radar speed trap, the wave undergoes two shifts: first when it hits the moving car, and second when it reflects back to the stationary radar gun.

RADAR GUN

MOVING VEHICLE (\( v \))

Sketch the wave pulses going out (Frequency \( f \)) and the pulses coming back (Frequency \( f' \)) if the car is speeding toward the radar.

Sketch wave patterns here

2

Color Doppler Imaging

Medical ultrasound uses the frequency shift of sound waves reflecting off blood cells to determine flow velocity.

Scenario:

A doctor uses a \( 5.0 \text{ MHz} \) ultrasound probe to check an artery. The blood is moving at \( 0.15 \text{ m/s} \) directly toward the probe. (Speed of sound in tissue \(\approx 1540 \text{ m/s}\)).

Critical Question:

Will the frequency of the echo be higher or lower than \( 5.0 \text{ MHz} \)? Explain your reasoning.

Note

In medical Doppler, red doesn't mean "arterial" and blue doesn't mean "venous"—they only indicate direction relative to the probe!

3

Comparing Technologies

Application	Type of Wave	What is moving?
Weather Radar
Police Radar
Fetal Heart Monitor

Doppler Tech

Doppler Applications Slides

Radar and Flow Worksheet

Real World Doppler Teacher Guide