CBSE Class 11 Waves Worksheet Set 01

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Question. A person standing symmetrically between two cliffs claps his hands and starts hearing a series of echoes at intervals of 1 sec. If speed of sound in air is 340 m/s, the distance between the parallel cliffs must be
(a) 340 m
(b) 680 m
(c) 1020 m
(d) 170 m

Answer: A

Question. An echo repeats two syllables. If the velocity of sound is 330 m/s, then the distance of the reflecting surface is
(a) 66.0 m
(b) 33.0 m
(c) 99.0 m
(d) 16.5 m

Answer: A

Question. At room temperaturre, velocity of sound in air at 10 atmospheric pressure and at 1 atmospheric pressure will be in the ratio
(a) 10 : 1
(b) 1 : 10
(c) 1 : 1
(d) cannot say

Answer: C

Question. If there are six loops for 1 m length in transverse mode of Melde’s experiment., the no. of loops in longitudinal mode under otherwise identical conditions would be
(a) 3
(b) 6
(c) 12
(d) 8

Answer: A

Question. Three transverse waves are represented by
y₁ = A cos (kx - ωt)
y₂ = A cos (kx + ωt)
y₃ = Acos (ky - ωt)
The combination of waves which can produce stationary waves is
(a) y₁ and y₂
(b) y₂ and y₃
(c) y₁ and y₃
(d) y₁, y₂ and y₃

Answer: A

Question. An organ pipe open at one end is vibrating in first overtone and is in resonance with another pipe open at both ends and vibrating in third harmonic. The ratio of length of two pipes is
(a) 1 : 2
(b) 4 : 1
(c) 8 : 3
(d) 3 : 8

Answer: A

Question. A series of ocean waves, each 5.0 m from crest to crest, moving past the observer at a rate of 2 waves per second, what is the velocity of ocean waves?
(a) 2.5 m/s
(b) 5.0 m/s
(c) 8.0 m/s
(d) 10.0 m/s

Answer: D

Question. If the ratio of maximum to minimum intensity in beats is 49, then the ratio of amplitudes of two progressive wave trains is
(a) 7 : 1
(b) 4 : 3
(c) 49 : 1
(d) 16 : 9

Answer: B

Question. There are three sources of sound of equal intensities and frequencies 400, 401 and 402 vibrations per second. The number of beats/sec is
(a) 0
(b) 1
(c) 3
(d) 2

Answer: B

Question. The equation y a sin 2π/λ(vt-x) is expression for
(a) stationary wave of single frequency along x-axis
(b) a simple harmonic motion
(c) a progressive wave of single frequency along x-axis
(d) the resultant of two SHMs of slightly different frequencies

Answer: C

Question. The apparent wavelength of the light from a star moving away from the earth is 0.2% more than its actual wavelength.
Then the velocity of the star is
(a) 6 × 10⁷ m/sec
(b) 6 × 10⁶ m/sec
(c) 6 × 10⁵ m/sec
(d) 6 × 10⁴ m/sec

Answer: C

Question. In a resonance column, first and second resonance are obtained at depths 22.7 cm and 70.2 cm. The third resonance will be obtained at a depth
(a) 117.7 cm
(b) 92.9 cm
(c) 115.5 cm
(d) 113.5 cm

Answer: A

Question. A fork of frequency 256 Hz resonates with a closed organ pipe of length 25.4 cm. If the length of pipe be increased by 2 mm, the number of beats/sec. will be
(a) 4
(b) 1
(c) 2
(d) 3

Answer: C

Question. A distant star which is moving away with a velocity of 106 m/sec is emitting a red line of frequency 4.5 × 10¹⁴ Hz. The observed frequency of this spectral line is
(a) 4.5 × 10⁸ Hz
(b) 4.485 × 10¹⁴ Hz
(c) 4.515 × 10¹⁴ Hz
(d) 4.5 × 10¹⁴ Hz

Answer: B

Question. The intensity level of sound wave is said to be 4 decibel. If the intensity of wave is doubled, then the intensity level of sound as expressed in decibel would be
(a) 8
(b) 16
(c) 7
(d) 14

Answer: C

Question. The equation y = Asin² (kx -ωt) represents a wave with
(a) amplitude A, frequency w/ 2π
(b) amplitude A/2, frequency ω/π
(c) amplitude 2A, frequency ω/ 4π
(d) it does not represent a wave motion

Answer: B

Question. A fork of unknown frequency gives four beats/sec when sounded with another of frequency 256. The fork is now loaded with a piece of wax and again four beats/sec are heard. Then the frequency of the unknown fork is
(a) 256 Hz
(b) 252 Hz
(c) 264 Hz
(d) 260 Hz

Answer: D

Question. A sound wave of frequency f travels horizontally to the right. It is reflected from a large vertical plane surface moving to left with a speed v. The speed of sound in medium is c. Then
(a) the number of wave striking the surface per second is f(c+v)/c
(b) the wavelength of reflected wave is c(c + v)/f (c + v)
(c) the frequency of the reflected wave is f(c - v)/(c - v) 
(d) the number of beats heard by a stationary listener to the left of the reflecting surface is vf/c-v

Answer: A

Question. A toothed wheel is rotating at 240 rpm and a post card is held against the teeth. If the pitch of the tone is 256 Hz, then the number of teeth on the rotating wheel is
(a) 256
(b) 128
(c) 64
(d) 32

Answer: C

Question. A person carrying a whistle emitting continuously a note of 272 Hz is running towards a reflecting surface with a speed of 18 km h–1. The speed of sound in air is 345 m s^–1. The number of beats heard by him is
(a) 4
(b) 6
(c) 8
(d) zero

Answer: C

Question. A closed pipe and an open pipe have their first overtones identical in frequency. Their lengths are in the ratio
(a) 1 : 2
(b) 2 : 3
(c) 3 : 4
(d) 4 : 5

Answer: C

Question. A progressive sound wave of frequency 500 Hz is travelling through air with a speed of 350 ms^–1. A compression maximum appears at a place at a given instant. The minimum time interval after which the rarefraction maximum occurs at the same point, is
(a) 200 s
(b) 1/250s
(c) 1/500s
(d) 1/1000s

Answer: D

Question. Which of the following changes at an antinode in a stationary wave?
(a) Density only
(b) Pressure only
(c) Both pressure and density
(d) Neither pressure nor density

Answer: D

Question. If two tuning forks A and B are sounded together, they produce 4 beats per sec. A is then slightly loaded with wax and same no. of beats/sec. are produced again. If frequency of A is 256, the frequency of B would be
(a) 250
(b) 262
(c) 252
(d) 260

Answer: C

Question. A uniform wire of length 20 m and weighing 5 kg hangs vertically. If g = 10 m/s², then the speed of transverse waves in the middle of the wire is
(a) 10 m/s
(b) 10 √2 m/s
(c) 4 m/s
(d) zero

Answer: A

Question. The fundamental frequency of an open organ pipe is 300 Hz. The first overtone of this pipe has same frequency as first overtone of a closed organ pipe. If speed of sound is 330 m/s, then the length of closed organ pipe is
(a) 41 cm
(b) 37 cm
(c) 31 cm
(d) 80 cm

Answer: A

Question. A wave disturbance in a medium is described by y(x,t) = 0.02 cos(50πt + π/2) cos(10 πx) where x and y ar in metre and t is in second. Which of the following is correct?
(a) A node occurs at x = 0.15 m
(b) An antinode occurs at x = 0.3 m
(c) The speed wave is 5 ms^–1
(d) The wavelength is 0.3 m

Answer: C

Question. Two waves represented by y1 = a sinwt and y² = a sin(ωt + Φ) with Φ = π/2 are superposed at any point at a particular instant. The resultant amplitude is
(a) a
(b) 4a
(c) √2a
(d) zero

Answer: C

Question. The threshold of hearing for the human ear is 10^–12 W m^–2. This is taken as the standard level. The intensity of sound is 1 Wm–2. It has intensity (in dB).
(a) 10¹² dB
(b) 12 dB
(c) 240 dB
(d) 120 dB

Answer:D

Question. In expressing sound intensity, we take 10^–12 W m^–2 as the reference level. For ordinary conversation, the intensity level is about 10–6 W m–2. Expressed in decibel, this is
(a) 106
(b) 6
(c) 60
(d) loge (106)

Answer: C
 

1. Explosions on other planets are not heard on earth. Why?

2. Why longitudinal waves are called pressure waves?

3. Why do tuning forks have two prongs?

4. A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 430 Hz source? Will this source be in resonance with the pipe if both the ends are open?

5. Can beats be produced in two light sources of nearly equal frequencies?

6. A person deep inside water cannot hear sound waves produces in air. Why?

7. If the splash is heard 4.23 seconds after a stone is dropped into a well. 78.4 metes deep, find the velocity of sound in air?

8. How roar of a lion can be differentiated from bucking of a mosquito?

9. Explain briefly the analytical method of formation of beats?

10. Give two cases in which there is no Doppler effect in sound?

11. The length of a sonometer wire between two fixed ends is 110cm. Where the two bridges should be placed so as to divide the wire into three segments whose fundamental frequencies are in the ratio of 1:2:3?

Click on link below to download CBSE Class 11 Waves Worksheet A.