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. emitted ultrasound pulses time between emitted pulses (a) A stationary bat emits an ultrasound pulse that is reflected from a moth. The bat detects the reflected pulse 36 ms later. Calculate the distance between the bat and the moth. speed of sound = 340 ms$^{-1}$ (b) The bat flies towards the moth. Explain why the bat must change the time between the emitted pulses as the distance between the bat and the moth decreases.

A-Level Edexcel Physics Progressive and stationary waves: Bats use a pulse-echo technique

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. emitted ultrasound pulses ... 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 based on the time for part (a)

96%

114 rated

Answer

To find the distance between the bat and the moth, we first note that the time mentioned (36 ms) includes the time for the sound to travel to the moth and back to the bat. Therefore, the time for one-way travel is:

$ext{Time (one way)} = \frac{36 \text{ ms}}{2} = 18 \text{ ms} = 0.018 \text{ s}$

Using the speed of sound (340 m/s), we can calculate the distance:

$ext{Distance} = \text{Speed} \times \text{Time} = 340 \text{ ms}^{-1} \times 0.018 \text{ s} = 6.12 \text{ m}$

Step 2

Explain why the bat must change the time between the emitted pulses as the distance between the bat and the moth decreases for part (b)

99%

104 rated

Answer

As the bat flies towards the moth, the distance between them decreases. Consequently, the time it takes for the sound waves to travel to the moth and back also decreases. If the bat continues to emit pulses at the same interval, the time between receiving the reflected pulses will become shorter than the time taken to emit them. Therefore, the bat must adjust the frequency and timing of its emitted pulses to accommodate this changing distance, ensuring that it can effectively use echolocation to detect the moth.

Bats use a pulse-echo technique to hunt for moths - Edexcel - A-Level Physics - Question 9 - 2023 - Paper 2

Worked Solution & Example Answer:Bats use a pulse-echo technique to hunt for moths - Edexcel - A-Level Physics - Question 9 - 2023 - Paper 2

Calculate the distance based on the time for part (a)

Explain why the bat must change the time between the emitted pulses as the distance between the bat and the moth decreases for part (b)

Join the A-Level students using SimpleStudy...