Sonar

[MedPR]

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A submarine uses active sonar that emits signals with frequency of 500Hz. Bats use active sonar to detect small insects. How does the bat's signal compare to the submarine's sonar?

A. Bat sonar must have a longer wavelength
B. Bat sonar must have a shorter wavelength
C. Bat sonar must have a lower frequency
D. Bat sonar must have a higher frequency

Answer: B










Question: How do you decide between D and B, especially under the circumstances that they tell you the submarine emits a specific frequency rather than telling you about the emitted wavelength?

 

[circulus vitios]

A shorter wavelength is needed because insects are smaller than submarines. It's true that a shorter wavelength necessarily means a higher frequency, but this answer is built off the answer of "a shorter wavelength."

 

[MedPR]

A shorter wavelength is needed because insects are smaller than submarines. It's true that a shorter wavelength necessarily means a higher frequency, but this answer is built off the answer of "a shorter wavelength."

I'm missing the part where you know how D is a better answer than B 😕

 

[milski]

The frequency will depend on the wavelength and the speed of propagation in the corresponding media. Without knowing the speed of sound in water and air you won't be able to tell which one will have higher frequency.

You do know that you need shorter wavelength to detect smaller obstacles.

 

[circulus vitios]

I'm missing the part where you know how D is a better answer than B 😕

What is your thought process behind B?