Topic outline

    • Sound

      Q1. Fill in the blanks.

                               i.        Time taken by an object to complete one oscillation is called time period.

                              ii.        Loudness is determined by the amplitude of vibration.

                             iii.        The unit of frequency is hertz (Hz).

                             iv.        Unwanted sound is called noise.

                             v.        Shrillness of a sound is determined by the frequency of vibration.

                            vi.        Higher the frequency of vibration, the higher is the pitch, and shriller is the sound.

               vii.        Sound which is pleasing to the ear is called musical sound.


      Q2. State True (T) or False (F).

                               i.        Sound cannot travel in vacuum. T

                              ii.        The number of oscillations per second of a vibrating object is called its time period. F

                             iii.        If the amplitude of vibration is large, sound is feeble. F

                             iv.        For human ears, the audible range is 20 Hz to 20,000 Hz. T

                              v.        The lower the frequency of vibration, the higher is the pitch. F

                            vi.        Unwanted or unpleasant sound is termed as music. F

               vii.        Noise pollution may cause partial hearing impairment. T

      Q3. Name one animal which can hear ultrasonic sounds.

      Ans. Dogs


      Q4. How is sound produced?

      Ans. Sound is produced by vibrating objects.


      Q5. How does an object produce sound?

      Ans. Sound is produced when an objects vibrates.


      Q6. Name the sound producing organ in humans.

      Ans. Voice box (larynx)


      Q7. Name the organs of hearing in our body.

      Ans. Our ears are the organs of hearing in our body.


      Q8. Name that part of ear which vibrates when outside sound falls on it.

      Ans. Eardrum vibrates when outside sound falls on it.


      Q9. Name the unit used to measure the loudness of sound.

      Ans. The loudness is expressed in a unit called decibel (dB).

      Q10. Name the quantity whose unit is 'hertz'.

      Ans. The unit of frequency is called “hertz”.


      Q11. Does any part of the body vibrate when we speak? Name the part.

      Ans. Yes, vocal chords vibrate when we speak.


      Q12. On what factor does the pitch of a sound depend?

      Ans. The frequency determines the shrillness or pitch of a sound.


      Q13. What is the name of passage in outer ear which carries sound waves to the eardrum?

      Ans. The sound is carried through the Ear canal.


      Q14. Choose the correct answer: Sound can travel through
      (a) gases only      (b) solids only
      (c) liquids only     (d) solids, liquids and gases.

      Ans. (d) solids, liquids and gases.


      Q15. Which of the following voices is likely to have minimum frequency?
      (a) Baby girl        (b) Baby boy
      (c) A man           (d) A woman

      Ans. (c) A man          

      Q16. What is frequency of oscillation?

      Ans. The number of oscillations per second is called the frequency of oscillation.


      Q17. What is the audible range of frequencies for human ears?

      Ans. For human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz.


      Q18. What is vibration?

      Ans. The to and fro or back and forth motion of an object is termed as vibration.


      Q19. How does a sound producing object differ from silent?

      Ans. A sound producing object vibrates while a silent does not. We can feel the vibrations by touching them.


      Q20. What brings the sound of a ringing telephone bell to our ears?

      Ans. The sound of a ringing telephone bell travel to our ears through the air in the room.


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