Assertion (A) : The speed of ultrasound waves is higher than supersonic waves.

Reason (R) : Supersonic is used for objects travelling with speed greater than speed of sound in air.

1. both A and R are true and R is the correct explanation of A
2. both A and R are true and R is not the correct explanation of A
3. assertion is false but reason is true
4. assertion is true but reason is false

assertion is false but reason is true

Explanation

Assertion (A) is false because ultrasound refers to sound waves with frequencies above 20,000 Hz, but they still travel at the speed of sound in a given medium while supersonic refers to objects moving faster than the speed of sound in air. So, the ultrasound does not have a speed higher than "supersonic"; in fact, supersonic objects exceed the speed of sound, while ultrasound is still sound, just at high frequency.

Reason (R) is true because supersonic word is used for objects which travel with a speed greater than the speed of sound in air (i.e., 330 m/s or Mach 1).