Question

2 Ultrasonic waves are those sound waves having frequency
between 20 hertz and 1000 hertz
between 1000 hertz and 20000 hertz
more than 20 kilohertz
less than 20 hertz

Answer 1

auditory sound is that sound which have its range from 20 hertz to 20 kilo hertz. while sound waves having frequency less than this are called infra sonic waves i.e having frequency less than 20 hertz.while waves having frequency greater than auditory sound are called ultra sonic waves that is their frequency is more than 20 kilo hertz.
looking at above options we see that A and B come into the range if auditory sound and D comes into the range of infrasonic waves.so the only option left is C.
therefore C is the right answer.
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