PhysicsChapter 4: Sound
Echo and Ranging
Introduction
Echoes can be used to measure distance. A sound pulse is sent toward an object. The sound reflects and returns. If the travel time is measured and sound speed is known: distance = vt/2 The factor 2 is necessary because the sound travels: source → target → source.
Definition
Sonar
**SONAR** uses sound waves, often ultrasound, to detect underwater objects and measure depth or distance.
Worked Example
Ultrasound pulse returns after: t = 0.10 s Speed in water: v = 1500 m/s Distance: d = vt/2 = 1500 × 0.102 = **75 m**
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Review the key facts, formulas and checks before you move on.Echo and Ranging
Sticky Notes · Quick Revision
RANGING
- Measure distance
FORMULA
- vt/2
SONAR
- Underwater sound ranging