Ncert – class 9- science – Chapter 11 – Sound 1 Welcome to your Ncert - class 9- science - Chapter 11 – Sound 1 1. 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 332.6 m/sec 290.5 m/sec 300.4 m/sec 326.7 m/sec None 2. Which of the following is not a property of ultrasound that makes it useful in medicine? High frequency The waves are transverse None of these Ability to travel along path even with obstacles None 3. 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 4. 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 2.5 m 2 m 1.25 m None 5. 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: 351 m 254 m 513 m 153 m None 6. 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 is absorbed by sand particles Sand does not vibrate Sound generated by the plate is more than the sand particles None 7. 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 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. 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. None 8. 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 : 0.176m 0.178m 0.0172m 0.0176m None 9. An echo is heard, if ____________ between the source and the reflector is atleast 17 m Distance Arc length Time None of these None 10. 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 720 Hz 180 Hz 360 Hz 90 Hz None 11. Which of these correctly represents the definition of frequency? The number of oscillations per minute The number of oscillations per second The number of oscillations per hour The number of oscillations per day None 12. Which of these is not a function of the ear drum? Vibrate when sound enters Comprehend the vibrations of any sound None of these Send vibrations to the inner ear 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? 4 2 3 6 None 14. 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. 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 Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1. Statement 1 is false but statement 2 is true None 15. 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 6.4km 8.8km 13.4km None 16. Sound waves are also called? Transverse waves Mechanical waves Microwaves Longitudinal waves None 17. Which of the following correctly describes a wave? None of these It is a motion It is a medium It is a disturbance None 18. Objects that have hard-to-reach places for cleaning are placed in _________ and ultrasound waves are sent there. acid solution basic solution cleaning solution salt solution None 19. The wavelength of sound from a tuning fork of frequency 330 Hz is nearly. Use speed of sound in air as 330 m/s 1000 cm 330 cm 100 cm 10 cm None 20. The nature of sound waves in gases is Electromagnetic Longitudinal Stationary Transverse 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.
