Consider the following statements. 1. The heart vibrates at infrasonic. 2. The speed of sound is more in gas than in liquid and solid. 3. Mach number is used to describe the speed of sound. 4. Ultrasonic sound has frequency more than 20,000 Hz. Of these statements.
(A) 1, 2 and 3 are correct
(B) 2, 3 and 4 are correct
(C) 1, 3 and 4 are correct
(D) 1, 2 and 4 are correct
Important Facts
1 is correct: Heartbeats are infrasonic (<20 Hz). 2 is incorrect: Sound speed is lowest in gas. 3 is correct: Mach number measures speed relative to sound speed. 4 is correct: Ultrasonic sound is >20,000 Hz.
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Related Question Facts
Infrasonic waves are inaudible to humans and useful in earthquake monitoring.
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