Very Short Answers - Sound, Science, Class 9 Notes | Study Class 9 Science by VP Classes - Class 9

Class 9: Very Short Answers - Sound, Science, Class 9 Notes | Study Class 9 Science by VP Classes - Class 9

The document Very Short Answers - Sound, Science, Class 9 Notes | Study Class 9 Science by VP Classes - Class 9 is a part of the Class 9 Course Class 9 Science by VP Classes.
All you need of Class 9 at this link: Class 9

Q1. Is sound wave longitudinal or transverse?
 Ans. 
Sound wave is longitudinal in nature.
 

Q2. What is the relation between frequency (ν) and time period of a sound wave?
 Ans. 
ν = (1/T) Frequency is inversely proportional to time period.
 

Q3. In which of the three media air, water or steel does sound travel the fastest?
 Ans.
Sound travels fastest in steel.
 

Q4. Which has a higher pitch—the sound of a whistle or that of a drum?
 Ans. 
The sound of whistle has higher pitch.
 

Q5. What is pitch?
 Ans. 
The way our brain interprets the frequency of an emitted sound is called the pitch.
 

Q6. How can we distinguish one sound from another having the same pitch and loudness?
 Ans. 
The quality or timber of sound helps us to distinguish one sound from another having the same pitch and loudness.
 

Q7. What is the audible range of frequency for human beings?
 Ans.
The audible range of frequencies for human beings is 20 Hz to 20,000 Hz.
 

Q8. What is one Hz?
 Ans
. Hz is the unit of frequency, called as Hertz. One Hertz is equal to one cycle per second.
 

Q9. Define speed of sound.
 Ans. 
The speed of sound is defined as the distance travelled per unit time by compression or rarefaction.
 

Q10. What is ‘note’ of sound?
 Ans. 
The sound produced due to a mixture of several frequencies is called a note, it is pleasant to listen to.
 

Q11. What is the time period of sound wave?
 Ans.
The time taken by two consecutive compressions or rarefactions to cross a fixed points is called the time period of the wave.


Q12. Find the frequency of a wave whose time period is 0.002 second.
 Ans.

Frequency = 1/time period

Frequenct = 1/0.002 = 500 Hz


Q13. What is the minimum distance required to hear distinct echo?
 Ans. 
The minimum distance of the obstacle from the source of sound should be 17.2 m.
 

Q14. What is reverberation?
 Ans
. The repeated reflection that results in the persistence of sound is called reverberation.
 

Q15. What is SONAR?
 Ans.
SONAR means Sound Navigation and Ranging. It is a device that uses ultrasonic waves to measure the distance, direction and speed of underwater objects by getting the reflection of sound.
 

Q16. What is ‘ultrasonic’ and ‘infrasonic’ sound wave?
 Ans. 
Sound waves with frequencies below the audible range (less than 20 Hz) are termed as ‘‘infrasonic’’ and those sound waves with frequencies above the audible range (more than 20000 Hz) are termed as ‘‘ultrasonic’’.
 

Q17. What should be the time interval between the originated sound and the reflected sound to be heard distinctly?
 Ans. 
To hear a distinct sound the time interval between the originated sound and the reflected sound must be at least 0.1 second.
 

Q18. What is the function of middle ear?
 Ans
. It amplifies the sound received by the external ear and passes it to the internal ear.
 

Q19. Why does sound become faint with distance?
 Ans.
As sound scatters when it travels with the longer distance its wavelength is unable to reach it becomes faint.
 

Q20. Give two applications of echo.
 Ans.
Sound is used in SONAR and in Ultrasonology.

The document Very Short Answers - Sound, Science, Class 9 Notes | Study Class 9 Science by VP Classes - Class 9 is a part of the Class 9 Course Class 9 Science by VP Classes.
All you need of Class 9 at this link: Class 9

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