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Bats use a pulse-echo technique to hunt for moths - Edexcel - A-Level Physics - Question 9 - 2023 - Paper 2
Question 9
Bats use a pulse-echo technique to hunt for moths. The bat emits a series of ultrasound pulses as shown on the oscilloscope trace below. A stationary bat emits an u... show full transcript
Worked Solution & Example Answer:Bats use a pulse-echo technique to hunt for moths - Edexcel - A-Level Physics - Question 9 - 2023 - Paper 2
Step 1
Calculate the distance between the bat and the moth
Answer
To find the distance between the bat and the moth, we can use the formula:
When the bat emits a pulse and detects it 36 ms later, this time includes the travel time of the sound to the moth and back. Therefore, the actual time taken for the pulse to reach the moth is half of 36 ms:
Now substituting the values into the distance formula:
Thus, the distance between the bat and the moth is 6.12 meters.
Step 2
Explain why the bat must change the time between the emitted pulses as the distance between the bat and the moth decreases
Answer
As the bat flies towards the moth, the distance between them decreases. This results in a shorter time for the emitted ultrasound pulses to reach the moth and return.
If the time between the emitted pulses remains constant, the bat may receive the echoes of the previous pulses while still emitting new ones. This overlap can cause confusion, making it difficult for the bat to interpret the echoes accurately.
To maintain effective hunting, the bat must therefore decrease the time interval between emitted pulses to ensure it receives clear and distinct echoes that correspond to its current distance from the moth.