Ncert – class 9- science – Chapter 11 – Sound 1 Welcome to your Ncert - class 9- science - Chapter 11 – Sound 1 1. 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. 1.25 m 2 m 0.5 m 2.5 m None 2. Which of the following correctly describes a wave? It is a motion None of these It is a disturbance It is a medium None 3. 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: 513 m 351 m 153 m 254 m None 4. The nature of sound waves in gases is Electromagnetic Stationary Transverse Longitudinal None 5. Which of these is not a function of the ear drum? Vibrate when sound enters Send vibrations to the inner ear Comprehend the vibrations of any sound None of these None 6. 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 supersonic sound waves. 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 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 7. Objects that have hard-to-reach places for cleaning are placed in _________ and ultrasound waves are sent there. cleaning solution acid solution salt solution basic solution None 8. 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 Can penetrate the wall Has a definite pitch Has a definite loudness Has a definite quality None 9. 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 10. 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 100 cm 330 cm 10 cm None 11. Which of these correctly represents the definition of frequency? The number of oscillations per day The number of oscillations per minute The number of oscillations per hour The number of oscillations per second None 12. 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 Sound generated by the plate is more than the sand particles Sand does not vibrate Vibration of metal plate is more than sand particles Sound is absorbed by sand particles 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 4 2 3 None 14. 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 360 Hz 180 Hz 90 Hz None 15. 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 : 0.178m 0.0172m 0.176m 0.0176m None 16. 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 13.4km 8.8km None 17. 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 300.4 m/sec 290.5 m/sec 326.7 m/sec None 18. 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 true but statement 2 is false 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. None 19. An echo is heard, if ____________ between the source and the reflector is atleast 17 m Arc length Distance Time None of these None 20. Sound waves are also called? Transverse waves Longitudinal waves Microwaves Mechanical waves 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.
