Ncert – class 9- science – Chapter 11 – Sound 1 Welcome to your Ncert - class 9- science - Chapter 11 – Sound 1 1. 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 2. 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 3. 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 Both statements 1 and 2 are true but statement 2 is not the correct explanation of statement 1. 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 4. 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 loudness Can penetrate the wall Has a definite pitch Has a definite quality None 5. 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 290.5 m/sec 326.7 m/sec 300.4 m/sec 332.6 m/sec 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. Which of the following correctly describes a wave? None of these It is a disturbance It is a motion It is a medium None 8. Which of these is not a function of the ear drum? Send vibrations to the inner ear Comprehend the vibrations of any sound Vibrate when sound enters None of these None 9. The nature of sound waves in gases is Electromagnetic Stationary Longitudinal Transverse None 10. Objects that have hard-to-reach places for cleaning are placed in _________ and ultrasound waves are sent there. salt solution cleaning solution basic solution acid solution None 11. 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. 2.5 m 2 m 0.5 m 1.25 m None 12. 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 second The number of oscillations per hour None 13. 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 360 Hz 720 Hz 90 Hz None 14. 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 6 3 2 None 15. 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 1000 cm 100 cm 10 cm None 16. Sound waves are also called? Transverse waves Longitudinal waves Microwaves Mechanical waves None 17. 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 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. 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. None 18. Which of the following is not a property of ultrasound that makes it useful in medicine? The waves are transverse Ability to travel along path even with obstacles High frequency None of these None 19. 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] 6.4km 4.4km 8.8km 13.4km None 20. An echo is heard, if ____________ between the source and the reflector is atleast 17 m Arc length Time None of these Distance 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.
