Ncert – class 9- science – Chapter 11 – Sound 1 Welcome to your Ncert - class 9- science - Chapter 11 – Sound 1 1. 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 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. These are supersonic sound waves. These are electromagnetic waves. None 2. 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 3. 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 0.176m 0.0172m 0.0176m None 4. 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 5. 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 Sound generated by the plate is more than the sand particles Sand does not vibrate None 6. 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 7. 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 90 Hz 360 Hz 720 Hz 180 Hz None 8. The nature of sound waves in gases is Electromagnetic Stationary Transverse Longitudinal None 9. 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 254 m 153 m None 10. Which of the following correctly describes a wave? None of these It is a medium It is a disturbance It is a motion 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 true but statement 2 is false Statement 1 is false but statement 2 is true 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. 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 6.4km 13.4km 8.8km None 13. 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 14. Which of the following is not a property of ultrasound that makes it useful in medicine? Ability to travel along path even with obstacles None of these High frequency The waves are transverse None 15. Which of these correctly represents the definition of frequency? The number of oscillations per second The number of oscillations per hour The number of oscillations per day The number of oscillations per minute None 16. 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? 2 4 3 6 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 326.7 m/sec 290.5 m/sec 300.4 m/sec 332.6 m/sec None 18. Sound waves are also called? Microwaves Longitudinal waves Mechanical waves Transverse waves None 19. An echo is heard, if ____________ between the source and the reflector is atleast 17 m Arc length None of these Distance Time None 20. 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 pitch Has a definite quality Has a definite loudness Can penetrate the wall 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.
