Q.1 Which of the following is not a mechanical wave?
Sound wave
Water wave
Seismic wave
Light wave
Explanation - Mechanical waves require a medium to travel, whereas light is an electromagnetic wave and can propagate in vacuum.
Correct answer is: Light wave
Q.2 The speed of sound is maximum in:
Air
Water
Steel
Vacuum
Explanation - Sound travels faster in solids due to higher density and elasticity. It cannot propagate in vacuum.
Correct answer is: Steel
Q.3 Which of the following quantities remains unchanged when a sound wave passes from one medium to another?
Wavelength
Velocity
Frequency
Amplitude
Explanation - Frequency of a wave is determined by the source and does not change with the medium.
Correct answer is: Frequency
Q.4 The relation between velocity (v), frequency (f), and wavelength (λ) is:
v = f/λ
v = λ/f
v = f × λ
v = λ − f
Explanation - The basic wave equation is v = f × λ, relating velocity, frequency, and wavelength.
Correct answer is: v = f × λ
Q.5 Which property of sound is responsible for the recognition of different voices?
Frequency
Pitch
Quality
Loudness
Explanation - The timbre or quality of sound enables us to distinguish between different voices even at the same pitch and loudness.
Correct answer is: Quality
Q.6 The time taken for one complete oscillation is called:
Frequency
Period
Amplitude
Phase
Explanation - Period is the reciprocal of frequency and represents the time taken for one oscillation.
Correct answer is: Period
Q.7 The SI unit of sound intensity is:
W/m²
dB
N/m²
J/m³
Explanation - Sound intensity is defined as power per unit area, and its SI unit is watt per square meter (W/m²).
Correct answer is: W/m²
Q.8 Ultrasonic waves have frequencies:
Less than 20 Hz
Between 20 Hz and 20 kHz
Above 20 kHz
Equal to 20 Hz
Explanation - Ultrasonic waves have frequencies higher than the human audible limit of 20 kHz.
Correct answer is: Above 20 kHz
Q.9 If the amplitude of a sound wave is doubled, its intensity becomes:
Doubled
Quadrupled
Halved
Unchanged
Explanation - Intensity of a wave is proportional to the square of amplitude. Doubling amplitude makes intensity four times.
Correct answer is: Quadrupled
Q.10 Which of the following waves is longitudinal?
Sound in air
Light waves
Radio waves
Water surface waves
Explanation - Sound in air propagates as compressions and rarefactions, making it a longitudinal wave.
Correct answer is: Sound in air
Q.11 The Doppler effect refers to:
Change in frequency due to source-observer motion
Change in wavelength due to medium
Change in amplitude with distance
Reflection of waves
Explanation - The Doppler effect is the apparent change in frequency due to relative motion between source and observer.
Correct answer is: Change in frequency due to source-observer motion
Q.12 In resonance, maximum energy is transferred when:
Driving frequency = Natural frequency
Driving frequency < Natural frequency
Driving frequency > Natural frequency
Driving frequency = Zero
Explanation - Resonance occurs when the driving frequency matches the natural frequency of the system.
Correct answer is: Driving frequency = Natural frequency
Q.13 Beats are produced due to:
Interference of two waves of slightly different frequencies
Reflection of sound
Resonance
Diffraction of waves
Explanation - Beats occur due to constructive and destructive interference of two waves of nearby frequencies.
Correct answer is: Interference of two waves of slightly different frequencies
Q.14 In a closed organ pipe, the fundamental frequency corresponds to:
Node at closed end, antinode at open end
Antinode at both ends
Node at both ends
Antinode at closed end, node at open end
Explanation - Closed organ pipes have a node at the closed end and an antinode at the open end for the fundamental frequency.
Correct answer is: Node at closed end, antinode at open end
Q.15 The speed of sound in air at 0°C is approximately:
273 m/s
300 m/s
331 m/s
343 m/s
Explanation - At 0°C, the speed of sound in air is about 331 m/s, and it increases with temperature.
Correct answer is: 331 m/s
Q.16 Which of the following can undergo diffraction most easily?
Light waves
Gamma rays
Microwaves
X-rays
Explanation - Diffraction is more significant when the wavelength is comparable to obstacle size. Microwaves have larger wavelengths compared to light or X-rays.
Correct answer is: Microwaves
Q.17 The loudness of sound is measured in:
W/m²
Decibel
Hertz
Pascal
Explanation - Loudness is measured on a logarithmic scale in decibels (dB).
Correct answer is: Decibel
Q.18 A tuning fork vibrating with frequency 256 Hz produces 4 beats per second with a given source. The frequency of the source may be:
252 Hz or 260 Hz
250 Hz or 258 Hz
260 Hz only
252 Hz only
Explanation - Beat frequency = |f1 – f2| = 4 Hz. Hence, source frequency = 256 ± 4.
Correct answer is: 252 Hz or 260 Hz
Q.19 Which of the following devices works on the principle of ultrasonic waves?
Stethoscope
Sonar
Loudspeaker
Microphone
Explanation - Sonar uses ultrasonic waves to detect underwater objects and measure depth.
Correct answer is: Sonar
Q.20 The echo of a sound is heard when the reflecting surface is at least:
17 m away
34 m away
50 m away
100 m away
Explanation - For echo perception, the time gap must be ≥ 0.1 s. With speed of sound ~340 m/s, distance = v × t / 2 = 17 m.
Correct answer is: 17 m away
Q.21 If the length of a sonometer wire is doubled, the fundamental frequency becomes:
Half
Double
Four times
Unchanged
Explanation - Frequency is inversely proportional to length of vibrating wire (f ∝ 1/L).
Correct answer is: Half
Q.22 Which characteristic of sound determines its pitch?
Amplitude
Frequency
Intensity
Quality
Explanation - Pitch of sound depends directly on its frequency.
Correct answer is: Frequency
Q.23 The condition for constructive interference is:
Path difference = (2n+1)λ/2
Path difference = nλ
Path difference = n/2 λ
Phase difference = π
Explanation - Constructive interference occurs when waves meet in phase, requiring path difference of nλ.
Correct answer is: Path difference = nλ
Q.24 The speed of sound in air increases with:
Decrease in temperature
Increase in humidity
Increase in pressure
Decrease in density
Explanation - Moist air is less dense than dry air, so sound travels faster in humid air.
Correct answer is: Increase in humidity
Q.25 When a sound wave passes through air, the physical quantity that oscillates is:
Air particle displacement
Pressure
Density
All of the above
Explanation - Sound waves in air involve oscillations of displacement, pressure, and density.
Correct answer is: All of the above