Learn › Homi Bhabha Exam · Physics › Sound
Sound — Homi Bhabha Exam Physics MCQs with Solutions
Free Homi Bhabha Exam Physics Sound MCQs with step-by-step solutions covering Nature & Propagation of Sound, Frequency & Amplitude, Echo & Reverberation, Human Ear Mechanism, Ultrasound Applications. Practise online on Prepizo — no login needed.
▶ Practise Sound online (free)
Subtopics
Sample questions with solutions
Q1 — Nature & Propagation of Sound · hard · theory
An electric bell ringing inside a sealed glass jar becomes inaudible as air is pumped out. This shows that sound:
A. is an electromagnetic wave
B. needs light to travel
C. cannot travel through vacuum ✓ Correct
D. travels faster in vacuum
Solution: With no air (medium) there are no particles to carry the compressions and rarefactions, so sound cannot propagate.
Q2 — Nature & Propagation of Sound · hard · theory
Sound travels fastest in:
A. solids ✓ Correct
B. liquids
C. vacuum
D. gases
Solution: Particles are most tightly packed in solids, so sound travels fastest in solids and slowest in gases (and not at all in vacuum).
Q3 — Nature & Propagation of Sound · hard · numerical
Sound takes 3 s to travel from a source to a listener 1020 m away. The speed of sound in that air is:
A. 3060 m/s
B. 306 m/s
C. 1020 m/s
D. 340 m/s ✓ Correct
Solution: Speed $= \dfrac{1020}{3} = 340$ m/s.
Q4 — Frequency & Amplitude · hard · numerical
A sound wave has a speed of 340 m/s and a frequency of 170 Hz. Its wavelength is:
A. 0.5 m
B. 510 m
C. 2.5 m
D. 2 m ✓ Correct
Solution: Wavelength $= \dfrac{v}{f} = \dfrac{340}{170} = 2$ m.
Q5 — Frequency & Amplitude · hard · numerical
The time period of a wave of frequency 250 Hz is:
A. 250 s
B. 0.04 s
C. 0.004 s ✓ Correct
D. 0.25 s
Solution: Time period $= \dfrac{1}{f} = \dfrac{1}{250} = 0.004$ s.
Q6 — Frequency & Amplitude · hard · theory
Two sounds have the same loudness, but one is shriller than the other. The shriller sound has a greater:
A. frequency ✓ Correct
B. speed
C. time period
D. amplitude
Solution: Shrillness (pitch) is decided by frequency; equal loudness means equal amplitude.
Q7 — Echo & Reverberation · hard · numerical
A person shouts towards a cliff and hears the echo after 3 s. If the speed of sound is 340 m/s, the distance of the cliff is:
A. 113 m
B. 1020 m
C. 340 m
D. 510 m ✓ Correct
Solution: Sound travels to the cliff and back: total distance $= 340 \times 3 = 1020$ m, so the cliff is $\dfrac{1020}{2} = 510$ m away.
Q8 — Echo & Reverberation · hard · theory
To hear a distinct echo, the reflecting surface must be at least about 17 m away because:
A. echoes need bright light
B. the surface must be very hard
C. sound travels very slowly
D. the ear can distinguish two sounds separated by at least 0.1 s ✓ Correct
Solution: The ear resolves sounds ~0.1 s apart; in 0.1 s sound travels 34 m (there and back), so the surface must be at least ~17 m away.
Q9 — Echo & Reverberation · hard · numerical
A ship sends an ultrasound pulse to the sea bed and receives the echo after 2 s. If the speed of sound in water is 1500 m/s, the depth of the sea is:
A. 1500 m ✓ Correct
B. 1000 m
C. 750 m
D. 3000 m
Solution: Total path $= 1500 \times 2 = 3000$ m; depth $= \dfrac{3000}{2} = 1500$ m (this method is SONAR).
Q10 — Human Ear Mechanism · hard · theory
The three tiny bones (ossicles) of the middle ear function to:
A. convert light to sound
B. produce sound
C. store sound
D. amplify and transmit the vibrations to the inner ear ✓ Correct
Solution: The hammer, anvil and stirrup amplify the eardrum's vibrations and pass them to the cochlea.
Q11 — Human Ear Mechanism · hard · theory
The correct path of sound through the ear is:
A. pinna → cochlea → eardrum → ossicles
B. cochlea → eardrum → pinna → nerve
C. eardrum → pinna → cochlea → ossicles
D. pinna → ear canal → eardrum → ossicles → cochlea → auditory nerve ✓ Correct
Solution: Sound is collected by the pinna, travels down the ear canal to the eardrum, is amplified by the ossicles, converted in the cochlea, and carried by the auditory nerve.
Q12 — Ultrasound Applications · hard · theory
Ultrasound is used to detect cracks inside metal blocks because it:
A. melts the metal
B. is audible to workers
C. passes straight through cracks unchanged
D. is reflected back from a crack (a change in medium) ✓ Correct
Solution: A crack is a gap that reflects the ultrasound, revealing the flaw that a solid block would not.
Q13 — Ultrasound Applications · hard · theory
Bats and dolphins navigate and locate prey mainly using:
A. infrasound only
B. their sense of smell
C. visible light
D. ultrasound echoes (echolocation) ✓ Correct
Solution: They emit ultrasonic pulses and interpret the echoes to locate obstacles and prey — echolocation.
Q14 — Nature & Propagation of Sound · medium · theory
Sound waves are:
A. electromagnetic waves
B. longitudinal mechanical waves that need a material medium ✓ Correct
C. transverse waves that travel through vacuum
D. waves that need no medium
Solution: Sound is a longitudinal mechanical wave; it needs particles of a medium (solid, liquid or gas) to travel.
Q15 — Nature & Propagation of Sound · medium · numerical
Sound travels 1500 m in water in 1 s. The speed of sound in water is:
A. 150 m/s
B. 750 m/s
C. 15000 m/s
D. 1500 m/s ✓ Correct
Solution: Speed $= \dfrac{\text{distance}}{\text{time}} = \dfrac{1500}{1} = 1500$ m/s.
Q16 — Nature & Propagation of Sound · medium · theory
The regions of high pressure/density in a sound wave travelling through air are called:
A. crests
B. compressions ✓ Correct
C. rarefactions
D. troughs
Solution: In a longitudinal sound wave, compressions are high-density regions and rarefactions are low-density regions.
Q17 — Frequency & Amplitude · medium · theory
The pitch (shrillness) of a sound depends on its:
A. amplitude
B. wavelength only
C. speed
D. frequency ✓ Correct
Solution: Higher frequency gives a higher pitch; loudness depends on amplitude.
Q18 — Frequency & Amplitude · medium · theory
The loudness of a sound depends on its:
A. frequency
B. amplitude ✓ Correct
C. pitch
D. speed
Solution: A larger amplitude means a louder sound; pitch depends on frequency.
Q19 — Frequency & Amplitude · medium · numerical
A tuning fork vibrates 480 times in 2 s. Its frequency is:
A. 120 Hz
B. 960 Hz
C. 480 Hz
D. 240 Hz ✓ Correct
Solution: Frequency $= \dfrac{\text{number of vibrations}}{\text{time}} = \dfrac{480}{2} = 240$ Hz.
Q20 — Echo & Reverberation · medium · theory
An echo is heard because sound is:
A. transmitted through the obstacle
B. absorbed by the obstacle
C. reflected back from a distant obstacle ✓ Correct
D. refracted through the air
Solution: An echo is the repetition of a sound caused by its reflection from a surface.
Q21 — Echo & Reverberation · medium · theory
The persistence of sound in a large hall due to repeated reflections is called:
A. diffraction
B. refraction
C. an echo
D. reverberation ✓ Correct
Solution: Reverberation is the prolonging of sound by multiple reflections before it dies out.
Q22 — Echo & Reverberation · medium · theory
The ceilings and walls of cinema halls are made of sound-absorbing materials to:
A. reduce reverberation ✓ Correct
B. reflect all sound
C. increase reverberation
D. increase the echo
Solution: Absorbing materials cut down repeated reflections, reducing reverberation so speech is clear.
Q23 — Human Ear Mechanism · medium · theory
The part of the human ear that vibrates when sound waves fall on it is the:
A. auditory nerve
B. pinna
C. eardrum (tympanic membrane) ✓ Correct
D. cochlea
Solution: Sound waves make the eardrum vibrate; these vibrations are then passed on and amplified.
Q24 — Human Ear Mechanism · medium · theory
The part of the ear that converts sound vibrations into electrical nerve signals is the:
A. ear canal
B. eardrum
C. cochlea ✓ Correct
D. pinna
Solution: The fluid-filled cochlea contains sensory cells that turn vibrations into nerve impulses sent to the brain.
Q25 — Human Ear Mechanism · medium · theory
The outer, funnel-shaped part of the ear that collects sound waves is the:
A. auditory nerve
B. eardrum
C. pinna ✓ Correct
D. cochlea
Solution: The pinna (outer ear) gathers sound and directs it into the ear canal.
Q26 — Human Ear Mechanism · medium · theory
The audible range of frequencies for a normal human ear is about:
A. 20 Hz to 20,000 Hz ✓ Correct
B. 1 Hz to 100 Hz
C. 0 Hz to 20 Hz
D. 20,000 Hz to 40,000 Hz
Solution: Humans hear roughly 20 Hz to 20 kHz; below is infrasound and above is ultrasound.
Q27 — Ultrasound Applications · medium · theory
Ultrasound consists of sound waves of frequency:
A. below 20 Hz
B. above 20,000 Hz ✓ Correct
C. between 20 Hz and 20,000 Hz
D. exactly 20,000 Hz
Solution: Ultrasound is sound above the human audible limit of 20 kHz.
Q28 — Ultrasound Applications · medium · theory
The technique used by ships to find the depth of the sea using ultrasound is called:
A. LASER
B. MRI
C. SONAR ✓ Correct
D. RADAR
Solution: SONAR (Sound Navigation And Ranging) uses ultrasound echoes to measure depth and detect objects underwater.
Q29 — Ultrasound Applications · medium · theory
In hospitals, ultrasound is commonly used to:
A. sterilise the whole body
B. image internal organs and a developing foetus (ultrasonography) ✓ Correct
C. treat fractures by heating
D. measure body temperature
Solution: Ultrasonography forms images of internal organs and the foetus using reflected ultrasound.
Q30 — Ultrasound Applications · medium · theory
Ultrasonic waves are used to clean spiral tubes and delicate machine parts because they can:
A. produce loud audible sound
B. dislodge dirt particles from hard-to-reach places by vibration ✓ Correct
C. dissolve all metals
D. generate electricity
Solution: High-frequency vibrations shake off dirt from otherwise inaccessible surfaces.