# CBSE Class 9 Science Exam 2020-21: NCERT Based Important Extra Questions (With Answers) Chapter 12 - Sound

CBSE: Get NCERT based important extra questions & answers of CBSE Class 9 Science (Chapter 12 - Sound). These questions and answers are important for the preparation of upcoming CBSE 9th Science Exam 2020-21

CBSE Class 9 Science Exam 2020-21: NCERT Based Important Extra Questions (With Answers) Chapter 12 - Sound

CBSE: Check NCERT based important extra questions & answers of CBSE Class 9 Science (Chapter 12 Sound). These questions and answers are important for the preparation of the upcoming CBSE Class 9 Science Exam 2020-21. These questions can be asked in the exam with slight modifications.

CBSE Class 9 Science Exam 2020-21: NCERT Based Important Extra Questions (With Answers) Chapter 12 - Sound

Question: What is SONAR?

The SONAR technique is used to determine the depth of the sea and to locate underwater hills, valleys, submarines, icebergs, sunken ships etc.

Question: Differentiate between infrasonic & ultrasonic sound waves?

Sound waves with frequencies below the audible range are termed “infrasonic” and those above the audible range are termed “ultrasonic”.

Question: Fill in the blanks

The distance between two consecutive compressions or two consecutive rarefactions is called the __________.

The distance between two consecutive compressions or two consecutive rarefactions is called the wavelength.

Question: Name two factors on which speed of sound primary depends?

The speed of sound depends primarily on the nature and the temperature of the transmitting medium.

Question: What is the frequency range that is audible to average human beings?

The audible range of hearing for average human beings is in the frequency range of 20 Hz – 20 kHz.

Question: Earthquake produces which kind of sound before the main shock wave begins

(a) ultrasound

(b) infrasound

(c) audible sound

(d) none of the above

(b) infrasound.

Question: In SONAR, we use

(a) ultrasonic waves

(b) infrasonic waves

(d) audible sound waves

(a) ultrasonic waves

Question: If any explosion takes place at the bottom of a lake, what type of shock waves in water will take place?

Longitudinal waves.

Question: Why do we hear the sound produced by the humming bees while the sound

vibrations of the pendulum are not heard?

Humming bees produce sound by vibrating their wings which is in the audible range. In case of pendulum the frequency is below 20 Hz which does not come in the audible range.

Question: Infrasound can be heard by

(a) dog

(b) bat

(c) rhinoceros

(d) human beings