Difference between revisions of "Echolocation"
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#The [[sound]] is detected. | #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]]. | : 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. | + | : An [[object]] can be made 'invisible' to [[echolocation]] if it [[Absorb (Physics)|absorbs]] the [[sound]] instead of [[reflect]]ing it. |
[[Echolocation]] is used by: | [[Echolocation]] is used by: | ||
| − | * | + | *Bats - To avoid obstacles when flying and to find [[prey]]. |
| − | * | + | *Dolphins - To locate [[prey]] and the size and shape of their surroundings. |
| − | * | + | *Boats - To find shoals of [[fish]] and to find the distance to the sea bed. |
| − | * | + | *Submarines - To navigate underwater detecting the sea bed and to locate ships. |
===Equation=== | ===Equation=== | ||
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<math>x = v \frac{t}{2}</math> | <math>x = v \frac{t}{2}</math> | ||
| − | Where | + | Where |
<math>v</math> = The [[speed]] of [[sound]] through that [[medium]]. | <math>v</math> = The [[speed]] of [[sound]] through that [[medium]]. | ||
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<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>\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 [[ | + | <math>x</math> = The [[distance]] between the [[emit]]ter and [[object]]. |
===Example Calculations=== | ===Example Calculations=== | ||
{| class="wikitable" | {| 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 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 | + | | 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''' | | style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities''' | ||
Latest revision as of 13:46, 7 June 2019
Key Stage 4
Meaning
Echolocation is a method for finding objects using reflected sound waves.
About Echolocation
Echolocation takes place in several steps:
- A sound is emitted.
- The sound travels until it hits an object.
- The sound is reflected by the object.
- The sound travels back to the emitter.
- 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 absorbs the sound instead of reflecting it.
Echolocation is used by:
- Bats - To avoid obstacles when flying and to find prey.
- Dolphins - To locate prey and the size and shape of their surroundings.
- Boats - To find shoals of fish and to find the distance to the sea bed.
- Submarines - To navigate underwater detecting the sea bed and to locate ships.
Equation
NB: You do not have to remember the equation in this form, but should be able to work it out for yourself and apply it.
Distance = (Speed) x (Time)/2
The time is divided by two because the sound wave must travel to the object and then back again to the detector.
\(x = v \frac{t}{2}\)
Where
\(v\) = The speed of sound through that medium.
\(\frac{t}{2}\) = The time taken for the sound to travel to the object or from the object back to the detector.
\(x\) = The distance between the emitter and object.
Example Calculations
| A fishing boat uses sonar to detect schools of fish beneath the boat. A sonar pulse is emitted and then received 0.042 seconds 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. | A bat uses sonar to locate its prey. The bat emits an ultrasound squeak which it hears reflected 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. |
| 1. State the known quantities
v = 1500m/s t = 0.042s |
1. State the known quantities
v = 340m/s t = 30ms = 30x10-3s |
| 2. Substitute the numbers into the equation and solve.
\(x = v \frac{t}{2}\) \(x = 1500 \frac{0.042}{2}\) \(x = 31.5m\) \(x \approx 32m\) |
2. Substitute the numbers into the equation and solve.
\(x = v \frac{t}{2}\) \(x = 340 \frac{30 \times 10^{-3}}{2}\) \(x = 5.1m\) |