CBSE Class 11 Physics Waves Worksheet Set A

Question. Doppler’s effect is not applicable for
(a) audio waves
(b) electromagnetic waves
(c) shock waves
(d) None of these

Answer: C

Question. Two sinusoidal plane waves of same frequency having intensities I₀ and 4 I₀ are travelling in the same direction. The resultant intensity at a point at which waves meet with a phase difference of zero radian is
(a) I₀
(b) 5 I₀
(c) 9 I₀
(d) 3 I0

Answer: C

Question. If the intensities of two interfering waves be I₁ and I₂, the contrast between maximum and minimum intensity is maximum, when
(a) I₁ > > I₂
(b) I₁ << I₂
(c) I₁ = I₂
(d) either I₁ or I₂ is zero

Answer: C

Question. Sound waves of length λ travelling with velocity v in a medium enter into another medium in which their velocity is 4 v. The wavelength in 2^nd medium is
(a) 4λ
(b) λ
(c) λ/4
(d) 16λ

Answer: A

Question. Two periodic waves of intensities I₁ and I₂ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is
(a) 2 (I₁ + I₂)
(b) I₁ + I₂
(c) (√I₁ +√I₂)²
(d) (√I₁ - √I₂)²

Answer: A

Question. Two tones of frequencies n₁ and n₂ are sounded together. The beats can be heard distinctly when
(a) 10 < (n₁ – n₂) < 20
(b) 5 < (n₁ – n₂) > 20
(c) 5 < (n₁ – n₂) < 20
(d) 0 < (n₁ – n₂) < 10

Answer: D

Question. The equation of a spherical progressive wave is
(a) y = a sin ωt
(b) y = a sin (ωt - kr)
(c) y = a/√2 sin(ωt kr) 
(d) y = a/r sin(ωt kr) 

Answer: D

Question. In the sonometer experiment, a tuning fork of frequency 256 Hz is in resonance with 0.4 m length of the wire when the iron load attached to free end of wire is 2 kg. If the load is immersed in water, the length of the wire in resonance would be (specific gravity of iron = 8)
(a) 0.37 m
(b) 0.43 m
(c) 0.31 m
(d) 0.2 m

Answer: A

Question. The velocity of sound in air is 330 m/s. The r.m.s. velocity of air molecules (g = 1.4) is approximately equal to
(a) 400 m/s
(b) 471.4 m/s
(c) 231 m/s
(d) 462 m/s

Answer: B

Question. The velocity of sound in hydrogen is 1224 m/s. Its velocity in a mixture of hydrogen and oxygen containing 4 parts by volume of hydrogen and 1 part oxygen is
(a) 1224 m/s
(b) 612 m/s
(c) 2448 m/s
(d) 306 m/s

Answer: B

Question. An open and closed organ pipe have the same length. The ratio of pth mode of frequency of vibration of two pipes is
(a) 1
(b) p
(c) p (2p + 1)
(d) 2 p/((2p -1)

Answer: D

Question. Sound waves are not transmitted to long distances because,
(a) they are absorbed by the atmosphere
(b) they have constant frequency
(c) the height of antenna required, should be very high
(d) velocity of sound waves is very less

Answer: A

Question. What is the effect of increase in temperature on the frequency of sound produced by an organ pipe?
(a) increases
(b) decreases
(c) no effect
(d) erratic change

Answer: A

Question. Shock waves are produced by objects
(a) carrying electric charge and vibrating
(b) vibrating with frequency greater than 20000 Hz
(c) vibrating with very large amplitude
(d) moving with a speed greater than that of sound in the medium

Answer: D

Question. The speed of sound in a medium depends on
(a) the elastic property but not on the inertia property
(b) the inertia property but not on the elastic property
(c) the elastic property as well as the inertia property
(d) neither the elastic property nor the inertia property

Answer: C

Question. Consider the three waves z₁, z₂ and z₃ as
z₁ = A sin (kx – ωt)
z₂ = A sin (kx + ωt)
z₃ = A sin (ky – ωt)
Which of the following represents a standing wave?
(a) z₁ + z₂
(b) z₂ + z₃
(c) z₃ + z₁
(d) z₁ + z₂ + z₃

Answer: A

Question. Two sound waves of equal intensity I produce beats. The maximum intensity of sound produced in beats will be
(a) I
(b) 2I
(c) 3I
(d) 4I

Answer: D

Question. The speed of sound in oxygen (O₂) at a certain temperature is 460 ms^–1. The speed of sound in helium (He) at the same temperature will be (assume both gases to be ideal)
(a) 460 ms^–1
(b) 500 ms^–1
(c) 650 ms^–1
(d) 330 ms^–1

Answer: B

Question. Frequencies of sound produced from an organ pipe open at both ends are
(a) only fundamental note
(b) only even harmonics
(c) only odd harmonics
(d) even and odd harmonics

Answer: D

Question. Each of the properties of sound listed in column A primarily depends on one of the quantitites in column B. Choose the matching pairs from two columns
Column A   Column B
Pitch            Waveform
Quality         Frequency
Loudness      Intensity
(a) Pitch-wave form; Quality-frequency; Loudnessintensity
(b) Pitch-frequency; Quality-wave form; Loudnessintensity
(c) Pitch-intensity; Quality-wave form; Loudnessfrequency
(d) Pitch-wave form; Quality-intensity; Loudnessfrequency

Answer: B

Question. When a tuning fork vibrates with 1.0 m or 1.05 m long wire of a sonometer, 5 beats per second are produced in each case. What will be the frequency of the tuning fork?
(a) 195
(b) 200
(c) 205
(d) 210

Answer: C

Question. The fundamental frequency of an organ pipe is 512 Hz. If its length is increased, then frequency will
(a) decrease
(b) increase
(c) remains same
(d) cannot be predicted

Answer: A

Question. The property of a medium necessary for wave propagation is
(a) inertia
(b) elasticity
(c) low resistance
(d) All of the above

Answer: D

Question. Sound waves are travelling in a medium whose adiabatic elasticity is E and isothermal elasticity E'. The velocity of sound waves is proportional to
(a) E'
(b) E
(c) √E'
(d) E/E'

Answer: B

Question. An organ pipe, open from both end produces 5 beats per second when vibrated with a source of frequency 200 Hz. The second harmonic of the same pipes produces 10 beats per second with a source of frequency 420 Hz. The fundamental frequency of organ pipe is
(a) 195 Hz
(b) 205 Hz
(c) 190 Hz
(d) 210 Hz

Answer: B

Question. The equation of a cylindrical progressive wave is
(a) y = a sin ωt
(b) y = a sin (ωt - kr)
(c) y = a/√r sin (ωt - kr)
(d) y = a/r sin (ωt - kr)

Answer: C

Question. A wave y = a sin (wt – kx) on a string meets with another wave producing a node at x = 0. Then the equation of the unknown wave is
(a) y = a sin (ωt + kx)
(b) y = –a sin (ωt + kx)
(c) y = a sin (ωt – kx)
(d) y = –a sin (ωt – kx)

Answer: B

Question. When a string is divided into three segments of length l₁, l₂, and l₃ the fundamental frequencies of these three segments are v₁, v₂ and v₃ respectively. The original fundamental frequency (v) of the string is 

Answer: C

Question. The equation of a plane progressive wave is y = 0.9 sin 4π[t - x/2] . When it is reflected at a rigid support, its amplitude becomes 2/3 of its previous value. The equation of the reflected wave is 

Answer: B

Question. If two waves of same frequency and same amplitude, on superposition, produce a resultant disturbance of the same amplitude, the wave differ in phase by
(a) π
(b) 2 π/3
(c) Zero
(d) π/3

Answer: B