## Chapter 8 topic WAVES

1. stationary waves only of discrete  set of frequencies are set up in medium. this fact is called
a. harmonics
b. overtones
c. quantization of frequencies
d. superposition of frequencies

2.newton calculated the velocity of the sound in air at S.T.P equal to
a.280 m/s
b.250 m/s
c.300 m/s
d.322 m/s

3.which one of the following properties of sound is affected by change in air temperature
a.frequency
b.amplitude
c.intensity
d.wavelength

4.the velocity of sound in air would become double than its velocity at200C is
a.313 K
b.586 K
c.899 K
d.1172 K

5.if 20 waves pass through the medium in 1 second with speed 20 m/s then the wavelength is
a.20 m
b.2 m
c.400 m
d.1 m

6.beats can be heard when difference of frequency is not more than
a.8
b.10
c.4

d.6

7.the system followed by newton for the determination of speed of sound in air is
b.isothermal
c.isobaric
d.isochoric

8.stars moving towards the earth show
a.red shift
b.blue shift
c.yellow shift
d.green shift

9.the speed of sound in air at S.T.P is 300 m/s.if the air pressure becomes double the temperature remains the same, the speed of sound would become
a.1200 m/s
b.600 m/s
c.300 under root 2 m/s
d.300 m/s

10.destructive interference occurs as
a.two waves that are in phase and moving in opposite direction meet
b.crests of two waves coincide and topple over
c.trough of two waves coincide
d.the crest of one wave coincides with the trough of an oncoming wave

11.what does a wave carry?
a.particles
b.energy
c.matter
d.heat

12.the speed pf sound in steel is greater than it is in air because steel is
a.more elastic than air
b.less elastic than air
c.more dense than air
d.less dense than air

13.a source produces sound with frequency of 1000 Hz.It moves away from the observer at a speed of sound.what frequency does the observer detect?
a.1000 Hz
b.500 Hz
c.less than 1 Hz
d.observer hears no sound

14.if the energy of longitudinal wave travels from south to north, the particle of medium move
a.from south to north only
b.both north and south
c.from east to west only
d.they are created by vibrating source

15.a set of 31 tuning forks is so arranged that each gives 5 beats per second with the previous one.if the frequency of last tuning fork is double to that of the  first, the frequency of third tuning fork is
a.250 Hz
b.220 Hz
c.160 Hz
d.150 Hz

16.in interference there is redistribution of
a.amplitude
b.frequency
c.phase
d.energy

17.doppler effect is independent of
a.distance between source and listener
b.velocity of source
c.velocity of listener
d.none of these

18.a source emits a sound of frequency 400 Hz but the listener hears it to be 300 Hz.because
a.the listener is moving toward the source
b.the source is  moving toward the listener
c.source is moving away from listener
d.the listener has a defective ear

19.the source and observer are moving toward each other with a speed equal to v / 2 where v is speed of sound.The source is emitting sound of frequency n,the frequency heard by the listener will be
a.zero
b.n
c.n / 3
d.3n

20.an observer moves towards a  stationary source of sound with speed 1 / 5th of the speed of sound.the wavelength and frequency of the source emitted are (lambda) and f respectively.the apparent frequency and the wavelength recorded by observer are respectively
a.1.2 f,lambda
b.f, 12 lambda
c.0.8f , 0.08 lambda
d.1.2 f , 1.2 lambda

21. the wavelength of fundamental mode of vibration og s closed pipe is
a. 2l
b.4l
c.l
d.l/2

22. the number of nodes between two consecutive anti nodes is
a. 0
b.3
c.1
d.2

23. what should be the velocity of sound source moving towards a stationary observer so the apparent frequency is double the actual frequency
a. v
b.v/2
c.2v
d.v/4

24.the distance between two consecutive nodes is
a.lambda by 2
b.lambda by 4
c.lambda
d.2 lambda