Sound

CLASS-VIII

SOUND

ASSIGNMENT-6

Q1. Fill in the blanks:

a)     Time taken by an object to complete one oscillation is called______________.

b)    Loudness is determined by the____________________ of vibration.

c)     The unit of frequency is____________.

d)    Unwanted sound is called_____________.

e)     Shrillness of a sound is determined by the_______________ of vibration.

f)      The three tiny bones present in the ear are_____________,____________ and______________.

g)     The effect of sound stays on the ear drum for about_________.

h)     __________is the minimum distance to hear an echo.

i)       Noise is produced by_______________ vibrations.

j)       For human ears the audible range is ___________ to ____________.

Q2. In which medium sound travels fastest: air, water or steel?

Q3. Name the type of waves which are used by astronauts to communicate with another on moon (or in outer space).

Q4. Which property of sound leads to the formation of echoes?

Q5. Choose the infrasonic waves and ultrasonic waves from the following frequencies:

a)     30,000 Hz

b)    18 Hz

c)     50,000 Hz

d)    10 Hz

Q6. Which of the following sound frequencies cannot be heard by a human ear?

a)     10 Hz

b)    100 Hz

c)     10,000 Hz

d)    15 Hz

e)     40,000 Hz

Q7. What type of sound waves is produced by a vibrating simple pendulum?

Q8. What is the name of the device which is used to find the depth of sea (or ocean) by using ultrasonic sound waves?

Q9. Name two animals which can produce ultrasonic waves.

Q10. Name the three characteristics of sound.

Q11. Name the characteristic which helps us distinguish between a man’s voice and a woman’s voice, even without seeing them.

Q12. A cricket ball is seen to hit the bat first and the sound of hitting is heard a little later. Why?

Q13. When we put our ear to a railway line, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through the air. Why?

Q14. On which day, a hot day or a cold day, an echo is heard sooner? Give reason for your answer.

Q15. Why should we not put a pin or a pencil in our ears?

Q16. What is the function of 3 tiny bones in the middle ear?

Q17. A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.

Q18. The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?

Q19. A man standing 825 metres away from a cliff fires a gun. After how long will he hear its echo? Speed of sound in air is 330m/s.

Q20. The echo of a sound is heard after 3seconds. If the speed of sound in air be 330m/s, calculate the distance of the reflecting surface.

Q21. What is meant by the quality of sound?

Q22. The quality of sound produced by men, women and children is different. Why?

Q23. Explain why, if we strike a tabla lightly , we hear a soft sound but if we hit the tabla hard, a lound sound is heard.

Q24. What is the difference between noise and music? Can music become noise sometimes?

Q25. List sources of noise pollution in your surroundings.