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Free Waves MCQs with Answers

1,281 Waves MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.

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Progressive WavesWave SpeedSpeed of SoundSuperposition and InterferenceStationary WavesOrgan PipesSimple Harmonic Motion
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1,281 questions · page 42 of 65

821. An observer moves with velocity 'vO' towards a stationary source, then the number of waves received in one second is:

  • A. A
  • B. B
  • C. C
  • D. D

Explanation: For a stationary source and an observer moving towards the source the equation is: 𝑓 ' = 𝑓( 𝑣+𝑣 0 𝑣 )

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Correct answer: C

822. In the case when the electrons lose all their kinetic energy (K.E.) in the first collision, the X-ray photon emitted has the following set of frequency and wavelength?

  • A. fmax , λmin
  • B. fmax , λmax
  • C. fmin , λmax
  • D. fmin , λmin

Explanation: fmax , λmin : This option suggests that when electrons lose all their kinetic energy in the first collision, the emitted X-ray photon will…

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Correct answer: fmax , λmin

823. The spectrum of a star's light is measured and the wavelength of one of the lines as the sodium's line is found to be 589 nm. The same line has the wavelength of 497 nm when observed in the laboratory. This means the star is:

  • A. Moving away from the earth
  • B. Moving towards the north
  • C. Stationary
  • D. Revolving around the planet

Explanation: When the wavelength of star was measured it resembled to the wavelength of sodium having wavelength 589 nm and when the sodium line was…

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Correct answer: Moving away from the earth

824. The wavelength ' λ' of a wave depends on the speed 'v' of the wave and its frequency 'f'. Decide which of the following is correct?

  • A. f = v λ
  • B. f = λ/v
  • C. f = v/λ
  • D. f = vλ2

Explanation: The relationship between wave speed (v), frequency (f), and wavelength (λ) is given by the equation v = fλ.

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Correct answer: f = v/λ

825. The speed of sound through a gas is measured as 340 m/s at pressure P1 and temperature T1. What will be the speed of sound if the pressure of a gas is doubled but the temperature is kept constant?

  • A. 342 m/s
  • B. 340 m/s
  • C. 170 m/s
  • D. 680 m/s

Explanation: According to laplace equation v=√(γP/p), the pressure and velocity are directly related however if the pressure is doubled then density…

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Correct answer: 340 m/s

826. A source of sound having a frequency "f" is moving with the velocity "u" towards a stationary listener. If "v'' is the velocity of the sound, then the apparent frequency of the sound heard by the observer would be:

  • A. vf / (v + u)
  • B. (v +u/v)f
  • C. vf/(v-u)
  • D. (v - u/v)f

Explanation: Doppler effect formula is= F0 = (v+v0/v +u) f f0= observed frequency v=velocity of sound in air (330m/s) u= velocity of the source v0=…

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Correct answer: vf/(v-u)

827. A source of sound moves towards a stationary observer with a speed one third of sound. If the frequency of the sound from the source is 100 Hz, the apparent frequency of the sound heard by the observer is:

  • A. 60 Hz
  • B. 100 Hz
  • C. 200 Hz
  • D. 150 Hz

Explanation: Doppler effect formula is=F0 = (v+v0/v +vs) fsf0= observed frequencyv=velocity of sound in air (330m/s)vs velocity of the sourcev0=…

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Correct answer: 150 Hz

828. For a certain organ pipe, three successive resonance frequencies are observed at 425, 595, and 765 Hz. The speed of the sound in air is 340 m/s. The pipe is:

  • A. Closed pipe of length 1 m
  • B. Closed pipe of length 2 m
  • C. Open pipe of length 1 m
  • D. Open pipe of length 2 m

Explanation: To find out which organ pipe is used, first, we will take the ratio of 3 observed harmonics: 425:595:765 5x 85 : 7x 85 : 9x 85 Since each…

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Correct answer: Closed pipe of length 1 m

829. A sound wave has a frequency of 2500 Hz and a speed of 1500 m s−1. What is the shortest distance from a point of maximum pressure in the wave to a point of minimum pressure?

  • A. 0.15 m
  • B. 0.30 m
  • C. 0.60 m
  • D. 1.20 m

Explanation: Frequency=2500 hzWave speed=1500m/sNow wave speed = wave length*FrequencySo wavelength=Wave speed/FrequencyWavelength=1500/2500 =3/5 =0.6…

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Correct answer: 0.30 m

830. Two wave sources are oscillating in phase. Each source produces a wave of wavelength 𝜆. The two waves from the sources meet at point 𝑋 with a phase difference of 90°.What is a possible difference in the distances from the two wave sources to point 𝑋?

  • A. 𝜆/8
  • B. 𝜆/4
  • C. 𝜆/2
  • D. 𝜆

Explanation: The two given sources are in phase. A distance equal to the wavelength corresponds to a phase difference of 360, this means that they are…

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Correct answer: 𝜆/4

831. If the wavelength of a transverse is 2cm and the period is 2 seconds, then the wave speed in CGS is:

  • A. 0.1 cms-1
  • B. 0.2 cms-1
  • C. 11 cms-1
  • D. 1 cms-1

Explanation: Option A, B & C are all numerically wrong.

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Correct answer: 1 cms-1

832. A wave of amplitude 20mm has intensity Ix. another wave of the same frequency but of amplitude 5mm has intensity Iy. What is Ix/Ty?

  • A. 2
  • B. 4
  • C. 16
  • D. 256

Explanation: The intensity of a wave is proportional to the square of its amplitude.

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Correct answer: 16

833. In a stationary wave the distance between consecutive antinodes is 25cm. If the wave velocity is 300ms-1, then the frequency of the wave will be:

  • A. 150 Hz
  • B. 300 Hz
  • C. 600 Hz
  • D. 750 Hz

Explanation: Distance between two consecutive antinodes is half the wavelength. We know that f=V/wavelength so 300/0.5 equals to 600.

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Correct answer: 600 Hz

834. When a car travelling with constant velocity passes a stationary observer, the observer hears a change in the frequency of sound emitted by the car. Which statement is correct ?

  • A. The change in frequency is greater as a car moves away than as it approaches.
  • B. The greater the speed of the car, the greater the change in observed frequency.
  • C. The observed frequency is lower as the car moves toward the observer and higher as the car moves away from the observer
  • D. The volume of the sound heard by the observer does not change as the car approaches.

Explanation: Wave speed is the distance a wave travels in a given amount of time, such as the number of meters it travels per second.

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Correct answer: The greater the speed of the car, the greater the change in observed frequency.

835. A tuning fork A produces 4 beats / second with another turning fork B of frequency 280 Hz. When fork A is loaded with a little wax, the beat frequency changes to 2. The frequency of fork A before loading is:

  • A. 292 Hz
  • B. 284 Hz
  • C. 290 Hz
  • D. 288 Hz

Explanation: Beat frequency is given by the equation; Beat frequency = f1-f2Whereas f1 is AAnd f2 is BSince the frequency of the B tuning fork is 280…

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Correct answer: 284 Hz

836. The sound waves of frequency more than 20 khz are termed as:

  • A. Supersonic
  • B. Audible
  • C. Infrasonic
  • D. Ultrasonic

Explanation: Ultrasonic waves are sound waves whose frequencies are higher than those of waves normally audible to the human ear.

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Correct answer: Ultrasonic

837. Velocity of sound in air is 332m/s. Velocity of sound in vacuum would be:

  • A. More than 332m/s
  • B. Less than 332m/s.
  • C. 332m/s
  • D. Zero

Explanation: Sound waves are longitudinal waves and they need a medium to travel. Thus, they cannot travel in vaccum.

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Correct answer: Zero

838. In frequency modulation, which of the following property of the original signal does not change:

  • A. Pitch
  • B. Frequency
  • C. Wavelength
  • D. Amplitude

Explanation: Frequency modulation is defined as changing the frequency of the carrier wave in accordance with the signals.

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Correct answer: Amplitude

839. In amplitude modulation, what remains the same:

  • A. Frequency of the wave
  • B. Amplitude of the wave
  • C. Wavelength of the wave
  • D. Intensity of waves

Explanation: In amplitude modulation, the amplitude of the carrier wave is altered in accordance with the amplitude of the modulating signal.

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Correct answer: Frequency of the wave

840. Example of mechanical waves is:

  • A. Transverse wave
  • B. Longitudinal wave
  • C. Both transverse and longitudinal wave
  • D. Compressional waves

Explanation: Mechanical Waves are waves which propagate through a material medium (solid, liquid, or gas) at a wave speed which depends on the elastic…

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Correct answer: Both transverse and longitudinal wave
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