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1. A wave that requires a material medium to travel is called
A. Mechanical wave
B. Electromagnetic wave
C. Matter wave
D. Standing wave
Answer: A. Mechanical wave
Explanation: Mechanical waves, such as sound and water waves, require a material medium (solid, liquid, or gas) to propagate.
2. In a transverse wave, the particles of the medium vibrate
A. Perpendicular to the direction of wave propagation
B. Parallel to the direction of wave propagation
C. In circles around a fixed point
D. Randomly with no fixed direction
Answer: A. Perpendicular to the direction of wave propagation
Explanation: In a transverse wave, particles of the medium oscillate perpendicular to the direction in which the wave travels, as seen in waves on a string.
3. In a longitudinal wave, the particles of the medium vibrate
A. Parallel to the direction of wave propagation
B. Perpendicular to the direction of wave propagation
C. In a circular path
D. They do not vibrate at all
Answer: A. Parallel to the direction of wave propagation
Explanation: In longitudinal waves like sound, particles oscillate back and forth along the same direction as the wave travels, creating compressions and rarefactions.
4. Sound waves in air are an example of
A. Longitudinal waves
B. Transverse waves
C. Electromagnetic waves
D. Standing waves only
Answer: A. Longitudinal waves
Explanation: Sound waves travel through air as longitudinal waves, with air molecules vibrating parallel to the direction of wave propagation, creating compressions and rarefactions.
5. The distance between two consecutive crests (or troughs) of a wave is called
A. Wavelength
B. Amplitude
C. Frequency
D. Time period
Answer: A. Wavelength
Explanation: Wavelength is the distance between two successive points in phase, such as two consecutive crests or troughs of a wave.
6. The relationship between wave speed (v), frequency (f), and wavelength (λ) is
A. v = fλ
B. v = f/λ
C. v = λ/f
D. v = f + λ
Answer: A. v = fλ
Explanation: The wave equation v = fλ relates the speed of a wave to its frequency and wavelength.
7. The speed of a transverse wave on a stretched string depends on
A. Tension in the string and its mass per unit length
B. Only the length of the string
C. Only the frequency of the source
D. The color of the string
Answer: A. Tension in the string and its mass per unit length
Explanation: The speed of a transverse wave on a string is given by v = √(T/μ), where T is tension and μ is mass per unit length, so it depends only on these two factors.
8. Sound travels faster in which medium?
A. Solids
B. Liquids
C. Gases
D. Vacuum
Answer: A. Solids
Explanation: Sound generally travels fastest in solids, slower in liquids, and slowest in gases, because the elastic modulus is much higher and particles are closer together in solids.
9. Sound cannot travel through
A. Vacuum
B. Solids
C. Liquids
D. Gases
Answer: A. Vacuum
Explanation: Being a mechanical wave, sound requires a material medium to travel and cannot propagate through vacuum, unlike electromagnetic waves.
10. When two waves overlap and their displacements add algebraically at every point, this is called
A. Principle of superposition
B. Doppler effect
C. Reflection
D. Refraction
Answer: A. Principle of superposition
Explanation: The principle of superposition states that when two or more waves overlap, the resultant displacement at any point equals the algebraic sum of the individual displacements.
11. A stationary (standing) wave is formed when
A. Two identical waves travel in opposite directions and superpose
B. A single wave travels through a medium without reflection
C. Two waves of different frequencies overlap
D. A wave passes through vacuum
Answer: A. Two identical waves travel in opposite directions and superpose
Explanation: Standing waves are formed by the superposition of two waves of the same frequency and amplitude traveling in opposite directions, such as an incident wave and its reflection.
12. In a standing wave, points that remain permanently at rest are called
A. Nodes
B. Antinodes
C. Crests
D. Troughs
Answer: A. Nodes
Explanation: Nodes are points in a standing wave pattern where the amplitude of vibration is always zero, as the two superposing waves cancel each other there.
13. In a standing wave, points of maximum vibration amplitude are called
A. Antinodes
B. Nodes
C. Wavefronts
D. Harmonics
Answer: A. Antinodes
Explanation: Antinodes are points on a standing wave where the two component waves reinforce each other, resulting in maximum amplitude of vibration.
14. Beats are produced when two sound waves of
A. Slightly different frequencies superpose
B. Exactly the same frequency and phase superpose
C. Widely different frequencies superpose
D. The same amplitude but travelling in the same direction meet
Answer: A. Slightly different frequencies superpose
Explanation: Beats arise from the superposition of two sound waves with slightly different frequencies, producing a periodic rise and fall in the loudness of the resultant sound.
15. The beat frequency produced by two waves of frequencies f₁ and f₂ is
A. |f₁ - f₂|
B. f₁ + f₂
C. f₁ × f₂
D. (f₁ + f₂)/2
Answer: A. |f₁ - f₂|
Explanation: The beat frequency equals the absolute difference between the two individual frequencies, |f₁ - f₂|.
16. Musicians use beats to
A. Tune musical instruments to the same frequency
B. Increase the loudness of a note permanently
C. Change the pitch of a note permanently
D. Eliminate all overtones from a note
Answer: A. Tune musical instruments to the same frequency
Explanation: Musicians listen for the beat frequency between two notes and adjust one instrument until the beats disappear, indicating both are at the same frequency.
17. The apparent change in frequency of a wave due to relative motion between the source and observer is called
A. Doppler effect
B. Interference
C. Diffraction
D. Polarization
Answer: A. Doppler effect
Explanation: The Doppler effect is the apparent change in the frequency of sound (or other waves) perceived by an observer due to the relative motion between the source and the observer.
18. When a sound source moves towards a stationary observer, the observed frequency
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: A. Increases
Explanation: As the source approaches the observer, successive wave crests are emitted closer together in space, effectively increasing the observed frequency (pitch), as heard in an approaching ambulance siren.
19. Why does the pitch of a train's whistle appear to drop as it passes and moves away from a stationary listener?
A. The Doppler effect causes the observed frequency to decrease as the source moves away
B. The train's whistle physically changes its own frequency
C. Sound waves travel slower when moving away
D. The wavelength of sound becomes zero
Answer: A. The Doppler effect causes the observed frequency to decrease as the source moves away
Explanation: As the source recedes, successive wave crests are stretched farther apart, lowering the observed frequency (pitch) heard by the stationary listener, a classic Doppler effect example.
20. The fundamental frequency of a stretched string fixed at both ends corresponds to
A. A standing wave with one antinode and two nodes at the ends
B. A standing wave with two antinodes and one node
C. No standing wave at all
D. A traveling wave with no reflection
Answer: A. A standing wave with one antinode and two nodes at the ends
Explanation: The fundamental mode (first harmonic) of a string fixed at both ends has nodes at the two ends and a single antinode at the center.
21. An open organ pipe supports which harmonics?
A. All harmonics (both even and odd)
B. Only odd harmonics
C. Only even harmonics
D. No harmonics at all
Answer: A. All harmonics (both even and odd)
Explanation: A pipe open at both ends supports all harmonics, since antinodes form at both open ends, allowing both even and odd multiples of the fundamental frequency.
22. A closed organ pipe (closed at one end) supports which harmonics?
A. Only odd harmonics
B. Only even harmonics
C. All harmonics equally
D. No harmonics
Answer: A. Only odd harmonics
Explanation: In a pipe closed at one end, a node forms at the closed end and an antinode at the open end, restricting the pipe to support only odd harmonics of the fundamental frequency.
23. The speed of sound in air increases with
A. Increasing temperature
B. Decreasing temperature
C. Increasing wavelength only
D. Decreasing frequency only
Answer: A. Increasing temperature
Explanation: The speed of sound in a gas increases with temperature, since higher temperature increases the average speed of gas molecules, allowing sound to propagate faster.
24. Reflection of sound waves that produces a repeated, distinctly heard sound is called
A. Echo
B. Resonance
C. Interference
D. Diffraction
Answer: A. Echo
Explanation: An echo is the repetition of sound caused by reflection from a distant surface, heard distinctly after a time delay due to the sound's travel and return.
25. For a human ear to distinguish an echo from the original sound, the reflecting surface must be at least approximately
A. 17 metres away
B. 1.7 metres away
C. 170 metres away
D. 0.17 metres away
Answer: A. 17 metres away
Explanation: Since the human ear can distinguish sounds separated by about 0.1 seconds, and sound travels at roughly 340 m/s, the minimum distance for a distinct echo works out to about 17 metres.
26. The energy carried by a wave is proportional to
A. The square of its amplitude
B. Its amplitude directly
C. The square root of its amplitude
D. Its wavelength only
Answer: A. The square of its amplitude
Explanation: The intensity (energy transported) of a wave is proportional to the square of its amplitude, so doubling the amplitude quadruples the energy carried.
27. The loudness of a sound is most closely related to its
A. Amplitude
B. Frequency
C. Wavelength
D. Speed
Answer: A. Amplitude
Explanation: The loudness of a sound is primarily determined by the amplitude of the sound wave; a larger amplitude corresponds to a louder sound.
28. The pitch of a sound is most closely related to its
A. Frequency
B. Amplitude
C. Speed
D. Intensity only
Answer: A. Frequency
Explanation: Pitch is the perceptual property of sound most closely associated with its frequency; higher frequency corresponds to a higher-pitched sound.
29. Why do we hear thunder a little after we see the lightning flash?
A. Light travels much faster than sound, so it reaches us almost instantly while sound takes longer
B. Thunder is produced after the lightning flash ends
C. Sound travels faster than light in air
D. Light and sound always travel together
Answer: A. Light travels much faster than sound, so it reaches us almost instantly while sound takes longer
Explanation: Since light travels at about 3 × 10⁸ m/s compared to sound's roughly 340 m/s in air, the flash of lightning is seen almost instantly, while the accompanying thunder, generated at the same time, takes noticeably longer to reach the observer.
30. Ultrasonic waves, used in applications like SONAR, have frequencies
A. Above the upper limit of human hearing (above about 20,000 Hz)
B. Below the lower limit of human hearing (below about 20 Hz)
C. Exactly equal to human speech frequencies
D. Within the audible range of humans
Answer: A. Above the upper limit of human hearing (above about 20,000 Hz)
Explanation: Ultrasonic waves have frequencies above 20,000 Hz, beyond the audible range for humans, and are used in applications like SONAR, medical imaging, and cleaning due to their high-frequency properties.
This page contains a chapter-wise objective practice set. Try the questions without checking the answer first, then use the explanation to understand the point you missed. The current page contains 30 questions, so you can practise in smaller sets when you are revising.
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