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What sound is produced by earthquakes before the main shock waves?

  1. ultrasound
  2. infrasound
  3. audible sound
  4. None of the above

Answer

b. infrasound

Earthquakes produce infrasound waves before the main shock waves.

 

In compression and rarefaction, pressure density is

  1. high and low respectively
  2. low and high respectively
  3. equal in both cases
  4. none of the above

Answer

a. high and low respectively

When a vibrating object moves forward in air as medium, it pushes and compresses the air in front of it creating a region of high pressure. This region is called a compression.

When a vibrating object moves backward in air as medium, it creates a region of low pressure. This region is called a rarefaction.

 

Stethoscope work on the principle of

  1. Ultrasound
  2. multiple reflections of sound
  3. both (a) and (b)
  4. None of the above

Answer

b. multiple reflection of sound

Add stethoscope reflection image

  1. Class 9
  2. Chapter 12 Class 9 - Sound

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.