Ncert – class 9- science – Chapter 11 – Sound 1 Welcome to your Ncert - class 9- science - Chapter 11 – Sound 1 1. Which of these correctly represents the definition of frequency? The number of oscillations per second The number of oscillations per minute The number of oscillations per hour The number of oscillations per day None 2. It is possible to recognise a person by hearing his voice even if he is hidden behind a wall. This is due to the fact that his voice Has a definite quality Can penetrate the wall Has a definite loudness Has a definite pitch None 3. A stone is dropped in a well which is 19.6m deep. Echo sound is heard after 2.06 sec (after dropping) then the velocity of sound is 300.4 m/sec 290.5 m/sec 326.7 m/sec 332.6 m/sec None 4. If the velocity of sound in a gas is 360 m/s and the distance between compression and the nearest rarefraction is 1m, then the frequency of sound is 180 Hz 90 Hz 360 Hz 720 Hz None 5. The nature of sound waves in gases is Electromagnetic Stationary Longitudinal Transverse None 6. A person can hear a sound of maximum frequency 20,000Hz, If the speed of sound in air is 344 ms −1 the wavelength is : 0.0176m 0.178m 0.0172m 0.176m None 7. Objects that have hard-to-reach places for cleaning are placed in _________ and ultrasound waves are sent there. salt solution basic solution acid solution cleaning solution None 8. An echo is returned in 3 s. If the speed of sound is 342 m/s, then the distance between the source of sound and the reflecting body is: 153 m 254 m 513 m 351 m None 9. The wavelength of sound from a tuning fork of frequency 330 Hz is nearly. Use speed of sound in air as 330 m/s 330 cm 10 cm 1000 cm 100 cm None 10. A long spring whose one end is fixed is stretched from the other end and then left longitudinal waves of frequency 500 Hz are produced. If the velocity of the wave is 250 m/s. Find the distance between two consecutive compressions and rarefaction. 0.5 m 2 m 1.25 m 2.5 m None 11. Statement 1: Loudness is the characteristic of a musical sound by which a loud sound can be distinguished from a faint sound.Statement 2: Echo is always produced when sound is incident on the hard and polished surface. Statement 1 is false but statement 2 is true Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1. Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1. Statement 1 is true but statement 2 is false None 12. A sound signal is simultaneously sent in air and water from a boat on a river. The echo of sound sent back by the river bed is heard in 4s, while the echo sent back by the aeroplane is heard in 8s. Find the distance between aeroplane and river bed.[velocity of sound in air =350m/s, velocity of sound in water =1500m/s] 4.4km 8.8km 6.4km 13.4km None 13. Two identical sounds A and B reach a point in the same phase. The resultant sound is C. The loudness of C is n dB higher than the loudness of A. The value of n is? 6 2 4 3 None 14. Sound waves are also called? Longitudinal waves Mechanical waves Microwaves Transverse waves None 15. Some whistles are designed to produce waves that can attract the attention of dogs but humans do not notice these waves. What kind of waves are these? These are normal sounds waves whose frequency is less than 20 � � 20 Hz. Humans cannot hear them because these waves have frequencies below the audible range. These are electromagnetic waves. These are normal sounds waves whose frequency is more than 20 , 000 � � 20,000 Hz. Humans cannot hear them because these waves have frequencies above the audible range. These are supersonic sound waves. None 16. A metallic spoon falls on a metal plate making a huge sound and upon bouncing from the plate, it falls on to the pile of sand below it with no noise being heard. Sound is not heard on sand because Vibration of metal plate is more than sand particles Sound generated by the plate is more than the sand particles Sand does not vibrate Sound is absorbed by sand particles None 17. Which of the following correctly describes a wave? It is a disturbance None of these It is a motion It is a medium None 18. An echo is heard, if ____________ between the source and the reflector is atleast 17 m Arc length None of these Distance Time None 19. Which of these is not a function of the ear drum? None of these Send vibrations to the inner ear Vibrate when sound enters Comprehend the vibrations of any sound None 20. Which of the following is not a property of ultrasound that makes it useful in medicine? None of these High frequency The waves are transverse Ability to travel along path even with obstacles None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
