Waves and Sound Practice Questions
20 free Waves and Sound practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
In which of the following types of waves do the particles of the medium vibrate parallel to the direction of wave propagation?
- A Transverse waves
- B Longitudinal waves
- C Electromagnetic waves
- D Surface waves
Correct answer: Longitudinal waves
Longitudinal waves, such as sound waves, consist of compressions and rarefactions where the medium's particles move back and forth along the same path that the wave travels. This is distinct from transverse waves, where the displacement is perpendicular to the wave's motion.
A sound wave travels from air into water. Which of the following properties of the wave remains unchanged?
- A Speed
- B Wavelength
- C Frequency
- D Amplitude
Correct answer: Frequency
The frequency of a wave is determined by the source and does not change when the wave enters a different medium. However, because the speed of sound is much higher in water than in air, the wavelength must increase to satisfy the wave equation v = fλ.
Which of the following determines the pitch of a musical sound?
- A Amplitude
- B Frequency
- C Velocity
- D Waveform
Correct answer: Frequency
Pitch is the human perception of frequency. High-frequency waves are perceived as high-pitched sounds, while low-frequency waves are perceived as low-pitched sounds.
What is the phenomenon called when two waves of slightly different frequencies interfere to produce a rhythmic variation in loudness?
- A Resonance
- B Doppler effect
- C Beats
- D Echo
Correct answer: Beats
Beats occur due to the constructive and destructive interference of two sound waves with nearly equal frequencies. The beat frequency is equal to the absolute difference between the two original frequencies.
An observer stands still as a police car with a siren approaches. The observer notices that the pitch of the siren sounds higher than it actually is. This is an example of:
- A Doppler effect
- B Rarefaction
- C Harmonic motion
- D Refraction
Correct answer: Doppler effect
The Doppler Effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. As the source approaches, wave fronts are compressed, leading to a higher perceived frequency.
In a transverse wave, the maximum displacement of a particle from its equilibrium position is called the:
- A Wavelength
- B Period
- C Amplitude
- D Crest
Correct answer: Amplitude
Amplitude measures the 'height' of the wave from the center line. It is directly related to the energy carried by the wave; in sound, it determines the loudness.
What is the range of frequencies that a typical healthy human ear can detect?
- A 2 Hz to 200 Hz
- B 20 Hz to 20,000 Hz
- C 200 Hz to 2,000,000 Hz
- D 20,000 Hz to 50,000 Hz
Correct answer: 20 Hz to 20,000 Hz
The audible range for humans is generally between 20 Hz and 20 kHz. Frequencies below 20 Hz are termed infrasonic, while those above 20 kHz are termed ultrasonic.
The speed of sound is generally fastest in which of the following media?
- A Vacuum
- B Gases
- C Liquids
- D Solids
Correct answer: Solids
Sound requires a medium to travel and moves faster through materials that are more rigid and less dense. Because solids have stronger intermolecular bonds and higher elasticity than liquids or gases, sound waves propagate through them most quickly.
A string of length L is fixed at both ends and vibrates in its fundamental mode. What is the wavelength of the standing wave produced?
- A L/2
- B L
- C 2L
- D 4L
Correct answer: 2L
In the fundamental mode (first harmonic), the string forms a single loop with nodes at both ends and one antinode in the middle. This loop represents half of a full wavelength, so the total wavelength is twice the length of the string (λ = 2L).
What happens to the intensity of a sound wave if the distance from the source is doubled?
- A It is reduced by half.
- B It becomes four times as large.
- C It is reduced to one-fourth.
- D It remains unchanged.
Correct answer: It is reduced to one-fourth.
Sound intensity follows the inverse square law, where Intensity ∝ 1/r². Doubling the distance (2r) results in the intensity being divided by 2 squared, which is 1/4 of the original intensity.
Which wave property is responsible for the 'echo' effect?
- A Refraction
- B Reflection
- C Diffraction
- D Polarization
Correct answer: Reflection
An echo is caused by the reflection of sound waves off a surface back to the listener. To hear a distinct echo, there must typically be at least 17.2 meters between the source and the reflecting surface.
When a sound wave enters a region where the air temperature is higher, what happens to its speed?
- A It increases.
- B It decreases.
- C It remains constant.
- D It becomes zero.
Correct answer: It increases.
The speed of sound in air is proportional to the square root of the absolute temperature. As temperature increases, air molecules move faster and transmit the vibrational energy of the sound wave more quickly.
Which of the following phenomena cannot be exhibited by sound waves?
- A Interference
- B Diffraction
- C Refraction
- D Polarization
Correct answer: Polarization
Polarization is a property that applies only to transverse waves, where the direction of oscillation is restricted. Since sound waves in air are longitudinal, they cannot be polarized.
What is the unit used to measure the intensity level of sound?
- A Hertz
- B Newton
- C Watt per square metre
- D Decibel
Correct answer: Decibel
The decibel (dB) is a logarithmic unit used to express the ratio of a sound's intensity to a reference intensity. It effectively maps the wide range of human hearing onto a manageable scale of 0 to 140+ dB.
A pipe closed at one end and open at the other can produce only which type of harmonics?
- A Odd-numbered harmonics
- B Even-numbered harmonics
- C All harmonics
- D The fundamental only
Correct answer: Odd-numbered harmonics
In a pipe closed at one end, the closed end must be a node and the open end an antinode. This boundary condition only allows for odd multiples of the fundamental frequency (1st, 3rd, 5th harmonics, etc.).
If the time period of a wave is 0.02 seconds, what is its frequency?
- A 50 Hz
- B 20 Hz
- C 100 Hz
- D 500 Hz
Correct answer: 50 Hz
Frequency is the reciprocal of the time period (f = 1/T). Therefore, f = 1 / 0.02, which equals 50 Hz.
The quality or 'timbre' of a sound depends on which of the following?
- A The fundamental frequency of the note
- B The amplitude of the pressure variation
- C The speed of the wave in the medium
- D The presence and strength of overtones
Correct answer: The presence and strength of overtones
Timbre is what allows us to distinguish between different musical instruments playing the same note. It is determined by the specific mix of harmonics and overtones produced alongside the fundamental frequency.
In a longitudinal wave, the regions of high pressure and high density are known as:
- A Troughs
- B Rarefactions
- C Nodes
- D Compressions
Correct answer: Compressions
Compressions are areas where the particles of the medium are pushed closest together, resulting in high pressure. Conversely, rarefactions are areas where the particles are spread farthest apart.
What occurs when the frequency of an external force matches the natural frequency of an object?
- A Resonance
- B Damping
- C Destructive interference
- D Refraction
Correct answer: Resonance
Resonance leads to a dramatic increase in the amplitude of vibration. This principle explains why a singer can shatter a wine glass or why soldiers must break step when crossing certain bridges.
Sonar (Sound Navigation and Ranging) primarily uses which type of waves to detect underwater objects?
- A Ultrasonic waves
- B Infrasonic waves
- C Radio waves
- D Visible light
Correct answer: Ultrasonic waves
Sonar utilizes ultrasonic waves because they have high frequencies and short wavelengths, allowing them to travel long distances through water and reflect off small objects with high precision.