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#The [[sound]] is detected.
: The time it takes the [[sound]] to return to its source can show how far away the [[object]] is located. Since the [[sound]] has to travel to the [[object]] and back again this time is twice as long as the time taken just to travel to the [[object]].
: An [[object]] can be made 'invisible' to [[echolocation]] if it [[Absorb (Physics)|absorbs]] the [[sound]] instead of [[reflect]]ing it.
[[Echolocation]] is used by:
*[[Bat]]s Bats - To avoid obstacles when flying and to find [[prey]].*[[Dolphin]]s Dolphins - To locate [[prey]] and the size and shape of their surroundings.*[[Boat]]s Boats - To find shoals of [[fish]] and to find the distance to the sea bed.*[[Submarine]]s Submarines - To navigate underwater detecting the sea bed and to locate [[ship]]sships.
===Equation===
<math>x = v \frac{t}{2}</math>
Where:
<math>v</math> = The [[speed]] of [[sound]] through that [[medium]].
<math>\frac{t}{2}</math> = The [[time]] taken for the [[sound]] to travel to the [[object]] or from the [[object]] back to the detector.
<math>x</math> = The [[distance]] between the [[emitteremit]] ter and [[object]].
===Example Calculations===
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |A fishing boat uses sonar to detect schools of fish beneath the boat. A sonar pulse is emitted and then received 0.042 [[second]]s later. The [[speed]] of [[sound]] in [[water]] is 1500m/s. Calculate how far beneath the boat the school of fish is located, correct to two [[Significant Figures|significant figures]].
| style="height:20px; width:300px; text-align:center;" |A bat uses sonar to locate its [[prey]]. The bat emits an [[ultrasound]] squeak which it hears [[reflect]]ed off its [[prey]] 30ms later. The [[speed]] of [[sound]] in [[air]] is 340m/s. Calculate the distance to the bats [[prey]], correct to two [[Significant Figures|significant figures]].
|-
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
v = 1500m/s
t = 0.042s
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
v = 340m/s
t = 30ms = 30x10<sup>-3</sup>s
|-
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>x = v \frac{t}{2}</math>
<math>x = 1500 \frac{0.042}{2}</math>
<math>x = 31.5m</math>
<math>x \approx 32m</math>
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>x = v \frac{t}{2}</math>
<math>x = 340 \frac{30 \times 10^{-3}}{2}</math>
<math>x = 5.1m</math>
|}