Below is a competitive-exam focused set on Sound, emphasizing everyday applications such as echo, SONAR, ultrasound, echolocation, noise control, megaphones, stethoscopes and Doppler effect.
1. An echo is produced mainly due to:
(A) Refraction of sound
(B) Reflection of sound
(C) Absorption of sound
(D) Diffraction of sound
Answer: (B) Reflection of sound
Explanation: An echo is the repetition of sound caused by reflection from a distant surface.
2. The repetition of a sound heard after it is reflected from a distant obstacle is called:
(A) Reverberation
(B) Echo
(C) Resonance
(D) Pitch
Answer: (B) Echo
3. Echoes are commonly heard in:
(A) Open fields without obstacles
(B) Large halls, mountains and empty buildings
(C) Vacuum
(D) Small rooms with thick carpets
Answer: (B) Large halls, mountains and empty buildings
4. The minimum time interval generally required for a distinct echo to be heard by the human ear is approximately:
(A) 0.01 s
(B) 0.1 s
(C) 1 s
(D) 10 s
Answer: (B) 0.1 s
5. SONAR is used mainly to:
(A) Measure atmospheric temperature
(B) Detect underwater objects and determine water depth
(C) Measure electric current
(D) Produce visible light
Answer: (B) Detect underwater objects and determine water depth
6. SONAR works mainly on the principle of:
(A) Refraction of light
(B) Reflection of ultrasonic waves
(C) Absorption of radio waves
(D) Reflection of visible light
Answer: (B) Reflection of ultrasonic waves
7. The full form of SONAR is:
(A) Sound Navigation and Ranging
(B) Sound Network and Radiation
(C) Sonic Navigation and Radio
(D) Sound Navigation and Resonance
Answer: (A) Sound Navigation and Ranging
8. SONAR is particularly useful for locating:
(A) Underground minerals only
(B) Underwater objects
(C) Clouds
(D) Stars
Answer: (B) Underwater objects
9. Medical ultrasonography uses:
(A) Infrared rays
(B) Ultraviolet rays
(C) Ultrasonic waves
(D) Radio waves
Answer: (C) Ultrasonic waves
10. Ultrasound is used in medical diagnosis mainly because it:
(A) Can travel only through vacuum
(B) Can produce images of internal body structures
(C) Is visible to the human eye
(D) Has no interaction with tissues
Answer: (B) Can produce images of internal body structures
11. Which of the following is a common application of ultrasound?
(A) Medical imaging
(B) Radio broadcasting
(C) Television transmission only
(D) Measuring electric current
Answer: (A) Medical imaging
12. Bats can fly and locate objects in darkness mainly by using:
(A) Infrared radiation
(B) Echolocation using ultrasonic sounds
(C) Radio waves
(D) Visible light
Answer: (B) Echolocation using ultrasonic sounds
13. Bats locate obstacles by:
(A) Producing sound and detecting its reflected echo
(B) Detecting Earth’s magnetic field only
(C) Producing visible light
(D) Measuring atmospheric pressure
Answer: (A) Producing sound and detecting its reflected echo
14. The sound frequencies used by bats for echolocation are generally:
(A) Infrasonic
(B) Ultrasonic
(C) Audible only
(D) Zero frequency
Answer: (B) Ultrasonic
15. A dog whistle can be heard by dogs but may not be heard by humans because it produces:
(A) Infrasonic sound
(B) Ultrasonic or very high-frequency sound
(C) Low-frequency audible sound
(D) No sound
Answer: (B) Ultrasonic or very high-frequency sound
16. The frequency of ultrasonic sound is:
(A) Below 20 Hz
(B) Between 20 Hz and 20,000 Hz
(C) Above approximately 20,000 Hz
(D) Exactly 20 Hz
Answer: (C) Above approximately 20,000 Hz
17. Soundproofing materials in recording studios are used mainly to:
(A) Increase sound reflection
(B) Absorb sound and reduce unwanted reflections
(C) Increase the speed of sound
(D) Increase pitch
Answer: (B) Absorb sound and reduce unwanted reflections
18. Materials such as carpets, curtains and acoustic panels are used in auditoriums mainly because they:
(A) Increase unwanted echoes
(B) Absorb sound and control reverberation
(C) Increase the frequency of sound
(D) Convert sound into electricity
Answer: (B) Absorb sound and control reverberation
19. Excessive reflection of sound inside a large auditorium can produce:
(A) Echoes and excessive reverberation
(B) Complete silence
(C) Lower atmospheric pressure
(D) Ultrasound
Answer: (A) Echoes and excessive reverberation
20. The design of a good auditorium generally aims to:
(A) Eliminate all sound
(B) Produce excessive reflection
(C) Provide suitable reflection and absorption of sound
(D) Prevent sound from reaching the audience
Answer: (C) Provide suitable reflection and absorption of sound
21. A megaphone helps a person speak to a large crowd mainly because it:
(A) Absorbs all sound
(B) Directs sound using reflection
(C) Converts sound into light
(D) Reduces the frequency to zero
Answer: (B) Directs sound using reflection
22. The conical shape of a megaphone helps:
(A) Spread sound equally in all directions
(B) Direct sound waves forward
(C) Absorb sound completely
(D) Convert sound into ultrasonic waves
Answer: (B) Direct sound waves forward
23. A stethoscope enables a doctor to hear internal body sounds mainly through:
(A) Reflection and transmission of sound
(B) Nuclear radiation
(C) Magnetic induction
(D) Refraction of light
Answer: (A) Reflection and transmission of sound
24. The tube of a stethoscope helps transmit sound from the patient’s body to the doctor’s ears by:
(A) Sound transmission through the enclosed passage
(B) Converting sound into light
(C) Producing ultrasound
(D) Blocking all sound
Answer: (A) Sound transmission through the enclosed passage
25. The Doppler effect refers to:
(A) Change in amplitude due to reflection
(B) Apparent change in frequency due to relative motion between source and observer
(C) Conversion of sound into heat
(D) Complete absorption of sound
Answer: (B) Apparent change in frequency due to relative motion between source and observer
26. When an ambulance approaches a stationary observer, the pitch of its siren appears:
(A) Lower
(B) Higher
(C) Unchanged
(D) Zero
Answer: (B) Higher
Explanation: As the source approaches, successive wavefronts reach the observer more frequently, increasing the observed frequency.
27. When an ambulance moves away from an observer, the observed pitch of its siren:
(A) Increases
(B) Decreases
(C) Remains unchanged
(D) Becomes ultrasonic
Answer: (B) Decreases
28. The apparent change in pitch of a moving train’s whistle as it passes an observer is an example of:
(A) Resonance
(B) Doppler effect
(C) Echo
(D) Reverberation
Answer: (B) Doppler effect
29. Which of the following is an application of the Doppler effect?
(A) Measuring the speed of moving objects
(B) Producing electricity in a generator
(C) Cooling water in an earthen pot
(D) Measuring atmospheric pressure
Answer: (A) Measuring the speed of moving objects
30. Which pair is correctly matched?
(A) Echo — Reflection of sound
(B) SONAR — Reflection of visible light
(C) Dog whistle — Infrasonic sound
(D) Doppler effect — Sound absorption
Answer: (A) Echo — Reflection of sound
31. Which of the following is incorrectly matched?
(A) Bats — Echolocation
(B) SONAR — Ultrasonic waves
(C) Medical ultrasound — Ultrasonic waves
(D) Dog whistle — Infrasonic waves
Answer: (D) Dog whistle — Infrasonic waves
32. A ship uses SONAR to determine the depth of the sea. The depth is calculated using the:
(A) Speed of sound and time taken for the echo to return
(B) Temperature of the ship
(C) Colour of seawater
(D) Atmospheric pressure only
Answer: (A) Speed of sound and time taken for the echo to return
33. Which type of sound cannot normally be heard by humans?
(A) Audible sound
(B) Ultrasonic sound
(C) Ordinary speech
(D) Musical sound
Answer: (B) Ultrasonic sound
34. Sound with a frequency below 20 Hz is called:
(A) Ultrasonic
(B) Infrasonic
(C) Audible
(D) Supersonic
Answer: (B) Infrasonic
35. Sound with a frequency above approximately 20,000 Hz is called:
(A) Infrasonic
(B) Ultrasonic
(C) Audible
(D) Subsonic
Answer: (B) Ultrasonic
36. Which of the following animals is well known for using ultrasonic echolocation?
(A) Bat
(B) Cow
(C) Elephant only
(D) Horse
Answer: (A) Bat
37. If a sound wave is reflected repeatedly inside a hall, the persistence of sound after the source stops is called:
(A) Reverberation
(B) Refraction
(C) Diffraction
(D) Polarization
Answer: (A) Reverberation
38. Which material would be most suitable for reducing unwanted sound in a room?
(A) Thick carpet
(B) Smooth metal sheet
(C) Glass plate
(D) Polished marble
Answer: (A) Thick carpet
39. Which of the following applications depends most directly on the reflection of sound?
(A) SONAR
(B) Electric motor
(C) Solar cell
(D) Thermos flask
Answer: (A) SONAR
40. Which sequence correctly matches the application with its principle?
(A) Echo — Reflection; SONAR — Ultrasonic reflection; Bats — Echolocation
(B) Echo — Refraction; SONAR — Conduction; Bats — Radiation
(C) Echo — Absorption; SONAR — Radiation; Bats — Conduction
(D) Echo — Diffraction; SONAR — Magnetism; Bats — Radiation
Answer: (A) Echo — Reflection; SONAR — Ultrasonic reflection; Bats — Echolocation
Quick Revision: Sound Applications
| Application | Principle |
|---|---|
| Echo | Reflection of sound |
| SONAR | Reflection of ultrasonic waves |
| Medical ultrasound | Ultrasonic waves |
| Bats | Ultrasound + echolocation |
| Dog whistle | High-frequency/ultrasonic sound |
| Noise reduction | Sound absorption |
| Auditorium | Reflection + absorption |
| Megaphone | Directional reflection of sound |
| Stethoscope | Sound transmission/reflection |
| Ambulance siren | Doppler effect |
| Moving train whistle | Doppler effect |
| Speed measurement | Doppler effect |
High-yield exam associations:
Echo → Reflection
SONAR → Ultrasonic + Reflection
Bats → Echolocation
Dog whistle → High frequency/Ultrasound
Medical imaging → Ultrasound
Carpet/curtain → Sound absorption
Auditorium → Controlled reflection + absorption
Megaphone → Directional reflection
Ambulance siren → Doppler effect