bat sonar vs submarine sonar

[keikoblue2]

Bats use active sonar to detect small insects. How does the bat's signal compare to the submarine's sonar?

TBR says the bat sonar must have a shorter wavelength because the insects are small. I used reflective index to reason that since air has n = 1, and water has n = 1.33, the wavelength in water is smaller than the wavelength in air. So I thought bat sonar must have a longer wavelength. How come this reasoning is wrong?

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[milski]

The n=1.33 refractive index is about light, it is not relevant to how sound waves propagate in any way.

The answer actually wants you to realize that the object needs to be similar or larger to the wavelength to reflect it. So, for smaller objects you need smaller wavelength. The media in this case does not matter.

 

[IcemanMD]

Wouldn't the sub sonar also be faster because water allows the sound to propagate faster?

 

[milski]

Wouldn't the sub sonar also be faster because water allows the sound to propagate faster?

Yes, that's also true. The OP did not post the possible answers but faster/slower was not a choice. Certainly not my favorite question but the idea behind it is reasonable.

 

[neurodoc]

You could have also figured it out by knowing that naval sonar is audible to the human ear and bat sonar is not (due to its much higher frequency).🙂