Question

1. Describe an activity to show that a sound wave is a mechanical wave and needs a material medium for its propagation.



2. What are compression and rarefaction called? What is the name given to the distance between two compressions? Write its expression.



3. (a) Differentiate between transverse waves and longitudinal waves. Give one example

Of each.

(b) Briefly explain how sound travels in air.



4. (a) Establish the relation between the speed of a sound wave and the frequency of a wave.

(b) A sound wave with a frequency of 5/2 Hz moves with a speed of 340m/s in air. What

Will be the speed of a sound wave of frequency 256Hz?



5. Define frequency, amplitude and speed of a sound wave.



6. Define the following characteristics of sound

(a)Pitch (b) Loudness (c) Quality



7. (a) Explain which wave property determines pitch. Define the property.

(b) Differentiate between tone and note.



8. The sound of a ringing bell inside a vacuum chamber can’t be heard. Why?



9. Three persons A, B and C are made to hear a sound travelling through different mediums

as given below:



Person A B C

Medium Iron rod Air Water



Who will hear the sound first? Why?



10. Why does the stage of an auditorium have curved backgrounds, curtains, carpets and false

Ceiling?

11. A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength

Of sound in a tissue in which the speed of sound is 1.7km/sec? The operating frequency

Of the scanner is 4.2MHz. (1MHz=10^6 Hz)



12. It is advised not to blow the horn near hospital area. Give reason.

 





13. (a) What is an echo? What are the conditions required to produce an echo?



(b) Am echo is heard on a day when temperature is about 220 c. Will the echo be heard?

Sooner or later if the temperature falls to 40 c.



14. A boy receives his echo after 3s. Find the distance of the reflection surface from the boy.

(Speed of sound in air is 342 m/s)



15. What is reverberation?



16. Ocean waves of time period 0.01 second have a speed of 15m/s. Calculate the

Wavelength of the waves. Find the distance between the adjacent crest and the trough.



17. Mention the audible range of frequencies for human beings. Differentiate between

Infrasonic and ultrasonic.



18. Briefly explain any two practical applications of ultrasonic waves.



19. Name two animals producing same type of waves created by earthquake.



20. What does SONAR stand for? Name its two main parts. List two uses of SONAR

Technique.



21. (a) A SONAR device on a submarine sends out a signal and receives an echo 5 seconds

later. Calculate the speed of sound in water if the distance of the object is 3625m.



(b) Explain how defects in a metal block can be detected using ultrasound.



22. Explain how human ear works in the transmission of sound wave to the brain.



23. Mr. Ravi Bhushan, father of Mr. Atul was hard of hearing. Doctor advice him to use

Hearing aid after diagnosing his ears. But he was not ready to listen to the advice of the

Doctor because he felt that hearing aid is machine and would cause harm to him. Mr.

Atul told his father that hearing aid is not harmful, rather it would help him. Finally

Mr. Ravi decided to have the hearing aid.

(a) What values are shown by Mr. Atul (b) on what principle hearing aid works?



24. Ram’s uncle felt echocardiography test is sensitive and he is not ready to have it. But

Ram prepared him for the test and told him the test helps the Doctor to know the

Condition of his heart. Finally his uncle convinced and had the echocardiography. The

Information helped the Doctor to treat him well.

(a) What is echocardiography? (b) What values are shown by Ram?​

Answer 1

Answer:

1.Bell-jar experiment demonstrates that sound needs a medium for its propagation. Take an electric bell and an airtight glass bell jar connected to a vacuum pump. Suspend the bell inside the jar, and press the switch of the bell. ... This shows that sound needs a material medium to travel.

Explanation: