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Q1. The maximum displacement of a vibrating body from its central position is called its:
Amplitude is the maximum displacement of a vibrating body from its mean (central) position. It determines the loudness of sound — larger amplitude means louder sound. Frequency is the number of vibrations per second, time period is the time for one vibration, and pitch is the shrillness or flatness of sound.
Q2. The number of oscillations or vibrations completed in one second is called the:
Frequency is the number of complete oscillations or vibrations made by a vibrating body in one second. It is measured in hertz (Hz). Amplitude is the maximum displacement, time period is the time for one oscillation, and loudness is the intensity of sound.
Q3. The time taken to complete one full oscillation is known as the:
The time period is the time taken to complete one full oscillation or vibration. It is the reciprocal of frequency. Amplitude is the maximum displacement, frequency is the number of oscillations per second, and hertz is the unit of frequency.
Q4. The SI unit of frequency is:
The SI unit of frequency is hertz (Hz), named after the German physicist Heinrich Hertz. One hertz means one oscillation per second. Decibel is the unit of loudness, meter is the unit of length, and second is the unit of time.
Q5. If an object vibrates 50 times in one second, its frequency is:
Frequency is the number of vibrations per second. If an object vibrates 50 times in one second, its frequency is 50 Hz. The other options are incorrect calculations or conversions.
Q6. The property of sound that distinguishes a shrill sound from a flat sound is called:
Pitch distinguishes a shrill (high-pitched) sound from a flat (low-pitched) sound. Pitch depends on frequency — higher frequency means higher pitch. Loudness depends on amplitude, and timbre is the quality that distinguishes different instruments.
Q7. A high-pitched sound has a:
A high-pitched sound has a high frequency. Frequency determines pitch: higher frequency means higher pitch. Amplitude determines loudness, not pitch. A low frequency would produce a low-pitched sound.
Q8. The loudness of sound is determined by its:
The loudness of sound is determined by its amplitude. Larger amplitude means louder sound. Frequency determines pitch, time period is the inverse of frequency, and speed is the rate at which sound travels.
Q9. The unit used to measure the loudness or sound level is the:
The decibel (dB) is the unit used to measure loudness or sound level. Hertz measures frequency, meter measures length, and second measures time. The decibel scale is logarithmic and used for sound intensity levels.
Q10. One complete to-and-fro motion of a vibrating object is called:
One complete to-and-fro motion of a vibrating object is called an oscillation (or vibration). Amplitude is the maximum displacement, frequency is the number of oscillations per second, and pitch is the shrillness or flatness of sound.
Q11. If the time period of a wave is 0.02 seconds, what is its frequency?
Frequency (f) = 1 / Time period (T). If T = 0.02 s, then f = 1/0.02 = 50 Hz. This means the wave completes 50 oscillations per second. The other options are incorrect calculations.
Q12. The pitch of a voice is high if the vocal cords are:
Short vocal cords vibrate quickly, producing a high pitch. Long vocal cords vibrate slowly and produce a low pitch. Loose and thick cords would produce a different quality of sound, not necessarily high pitch. The pitch depends on the frequency of vibration.
Q13. The loudness of normal breathing is approximately:
Normal breathing has a sound level of about 10 dB, which is very soft. A whisper is about 30 dB, normal conversation is around 60 dB, and busy traffic is around 70 dB. The decibel scale is logarithmic, so 10 dB is the softest sound.
Q14. A soft whisper heard from a distance of 5 meters is about:
A soft whisper heard from a distance of 5 meters is about 30 dB. This is louder than normal breathing but much softer than normal conversation (60 dB) or busy traffic (70 dB). The loudness decreases with distance.
Q15. The sound of busy traffic is typically around:
The sound of busy traffic is typically around 70 dB. This is considered moderately loud. Normal conversation is about 60 dB, and a whisper is about 30 dB. Factory noise can be around 80 dB or more.
Q16. The noise level in an average factory is approximately:
The noise level in an average factory is around 80 dB. This level can be harmful with prolonged exposure. The threshold for pain is about 120 dB. Busy traffic is about 70 dB, and normal conversation is 60 dB.
Q17. Sounds with frequencies above 20,000 Hz are called:
Sounds with frequencies above 20,000 Hz are called ultrasonic. These are beyond the human hearing range. Infrasonic sounds are below 20 Hz, audible sounds are between 20 Hz and 20,000 Hz, and supersonic refers to speeds faster than sound.
Q18. Sounds with frequencies below 20 Hz are called:
Sounds with frequencies below 20 Hz are called infrasonic. These are also beyond the human hearing range. Ultrasonic sounds are above 20,000 Hz, audible sounds are in the middle, and supersonic refers to speed, not frequency.
Q19. The range of audible frequencies for a healthy human ear is approximately:
A healthy human ear can hear sounds in the range of 20 Hz to 20,000 Hz (20 kHz). Frequencies below 20 Hz are infrasonic, and above 20,000 Hz are ultrasonic. This range may vary with age and hearing health.
Q20. Which of the following animals can hear ultrasonic sounds?
Dogs can hear ultrasonic sounds up to about 40,000–60,000 Hz. Elephants hear infrasonic sounds, and giraffes and pigeons have hearing ranges similar to humans or lower. Dogs are known for their ability to hear high-frequency sounds.
Q21. A sound that is unwanted or unpleasant to the ear is called:
Unwanted or unpleasant sound is called noise. Music is organized sound that is pleasant to hear. Pitch is the highness or lowness of a sound, and tone is a sound with a definite frequency. Noise pollution is a major environmental issue.
Q22. Which of the following sounds would be considered noise pollution?
Heavy machinery sound in a residential area at night is noise pollution. Birds chirping, lullabies, and flowing water are pleasant sounds. Noise pollution is unwanted sound that disturbs the environment and health.
Q23. Prolonged exposure to noise pollution can cause:
Prolonged exposure to noise pollution can cause hearing loss. It can also lead to stress, hypertension, and sleep disturbances. It does not improve hearing, increase appetite, or improve eyesight. Hearing loss is a serious health hazard of noise pollution.
Q24. The term that refers to how “shrill” or “flat” a sound is, is called:
Pitch refers to how “shrill” (high pitch) or “flat” (low pitch) a sound is. It depends on the frequency of the sound wave. Loudness is about intensity, amplitude is the displacement, and decibel is the unit of sound level. Pitch is the correct term.
Q25. The frequency of a wave is 20 Hz. Its time period will be:
Time period (T) = 1 / Frequency (f). If f = 20 Hz, T = 1/20 = 0.05 seconds. This is the time for one complete oscillation. The other options are incorrect calculations.
Q26. The loudness of sound is NOT affected by the:
Loudness is affected by amplitude, distance, and surface area (which affects how much air is set into motion). Frequency determines pitch, not loudness. So loudness is not affected by frequency, although it may be slightly influenced by frequency in some contexts.
Q27. Bats navigate and find food by emitting:
Bats emit ultrasonic waves (above 20,000 Hz) to navigate and find food using echolocation. The reflected waves help them detect obstacles and prey. Infrasonic waves are used by elephants, and radio waves are electromagnetic.
Q28. Elephants can communicate over long distances using:
Elephants communicate over long distances using infrasonic sounds (below 20 Hz). These low-frequency sounds travel long distances through the ground and air. Ultrasonic sounds are used by bats, and audible screams and visual signals are less effective over long distances.
Q29. One oscillation is also known as one:
One oscillation is also known as one vibration. Both terms refer to one complete to-and-fro motion. Hertz is the unit of frequency, decibel is the unit of loudness, and amplitude is the maximum displacement. So, vibration is the correct term.
Q30. The speed or frequency of vibration (how fast the object is moving back and forth) determines the:
The speed of vibration (frequency) determines the pitch of the sound. Higher frequency means higher pitch. Loudness is determined by amplitude, quality by waveform, and intensity by energy. Pitch is the correct characteristic.
Q31. Which of the following is NOT a hazard of noise pollution?
Noise pollution causes hypertension, insomnia, and stress, but it does not increase concentration. In fact, it reduces concentration and productivity. Noise pollution is harmful to both physical and mental health.
Q32. 1 Hertz is equal to:
1 Hertz (Hz) is equal to one oscillation or vibration per second. This is the SI unit of frequency. The other options are incorrect conversions. One oscillation per minute would be 1/60 Hz, and 10 or 100 oscillations per second would be 10 Hz or 100 Hz.
Q33. If the amplitude of a wave is doubled, the loudness becomes:
Loudness is proportional to the square of the amplitude. If amplitude is doubled, loudness increases by four times. It does not double or remain the same. This is because the energy of the wave is proportional to the square of the amplitude.
Q34. The eardrum of a person can be damaged if exposed to sound louder than:
Sound louder than 120 dB can cause pain and damage to the eardrum. This is considered the threshold of pain. Normal conversation is about 60 dB, and factory noise is about 80 dB. Prolonged exposure above 80 dB can also be harmful, but immediate damage occurs around 120 dB.
Q35. Which animal can hear the highest frequency of sound (up to 150,000 Hz)?
Dolphins can hear sounds up to about 150,000 Hz (150 kHz). Dogs can hear up to about 40,000–60,000 Hz, cats up to about 64,000 Hz, and elephants hear infrasonic sounds. Dolphins use ultrasonic sounds for echolocation.
Q36. The persistence of sound in a large hall due to multiple reflections is called:
Reverberation is the persistence or prolongation of sound in a hall due to multiple reflections. Echo is a distinct repetition of sound caused by reflection from a distant surface. Reverberation is common in large halls and can interfere with clarity of sound.
Q37. Sound becomes harmful noise pollution for humans at levels above:
Prolonged exposure to sound above 80 dB can be harmful and is considered noise pollution. Below 80 dB is generally safe for extended periods. Above 100 dB can cause immediate discomfort and damage. The threshold for hearing damage is around 80–85 dB over time.
Q38. The quality or timbre of sound helps us to:
Timbre (quality) helps us distinguish between two sounds of the same pitch and loudness produced by different instruments. It depends on the waveform and overtones. This is why we can tell a flute from a violin even when they play the same note.
Q39. If the time period of a vibration is 0.001 seconds, the frequency is:
Frequency (f) = 1 / Time period (T). If T = 0.001 s, f = 1/0.001 = 1000 Hz. This means the vibration completes 1000 oscillations per second. The other options are incorrect calculations.
Q40. Which of the following is a source of noise pollution in an urban environment?
Vehicles honking in traffic is a source of noise pollution in urban areas. School bells are temporary and not typically considered pollution, birds singing and water dripping are natural and pleasant sounds. Traffic noise is a major environmental concern.
Q41. A mosquito produces sound by beating its wings at a high frequency. This sound is:
A mosquito produces a high-pitched sound because its wings beat at a high frequency. The high frequency results in a shrill, high-pitched sound. Although it may also be soft, the pitch is high. The sound is audible to humans.
Q42. The magnitude of sound is measured in decibels. This is a measure of a sound wave’s:
Decibels measure the loudness of sound, which is related to the amplitude of the sound wave. Larger amplitude means more energy and louder sound. Frequency is measured in hertz, time period in seconds, and speed in meters per second. Loudness is amplitude-dependent.
Q43. Which of the following can be a hazard of long-term exposure to noise pollution, other than hearing loss?
Long-term exposure to noise pollution can cause increased stress, anxiety, and even hypertension. It does not improve sleep, lower blood pressure, or improve concentration. Noise pollution is a serious health risk affecting mental and physical well-being.
Q44. The frequency of a sound wave is 10,000 Hz. This sound is:
A frequency of 10,000 Hz is within the human hearing range of 20 Hz to 20,000 Hz, so it is audible. Infrasonic is below 20 Hz, ultrasonic is above 20,000 Hz, and supersonic refers to speed. 10,000 Hz is clearly audible.
Q45. A complete back-and-forth movement of a pendulum from its starting point is:
A complete back-and-forth movement of a pendulum from its starting point and back is one oscillation (or one vibration). Frequency is the number of oscillations per second, hertz is the unit, and amplitude is the maximum displacement. So, oscillation is the correct term.
Q46. The maximum sound level that a human ear can tolerate without feeling pain is about:
The threshold of pain for the human ear is about 120 dB. Above this level, sound can cause immediate pain and damage. 60 dB is normal conversation, 80 dB is factory noise, and 100 dB is a loud rock concert. 120 dB is the pain threshold.
Q47. The voice of a lion is low-pitched because its vocal cords are:
A lion’s voice is low-pitched because its vocal cords are long and vibrate slowly. Longer cords produce lower frequencies, resulting in a deeper, low-pitched sound. Short cords produce high pitch, and thin or tight cords affect quality, not necessarily pitch.
Q48. Unwanted sound in the environment that causes health issues is called:
Unwanted sound that causes health issues is called noise pollution. It is a major environmental problem that affects hearing, mental health, and overall well-being. Music can be pleasant, ultrasound is high-frequency sound, and frequency is a physical property.
Q49. The loudness of a sound of a source decreases when we move away from it because:
The loudness of sound decreases with distance because the amplitude of the sound wave decreases as it spreads out. Frequency and pitch do not change with distance, and speed remains constant in a given medium. Amplitude reduction is the reason for decreased loudness.
Q50. Infrasonic sound can be produced by:
Earthquakes produce infrasonic sounds (below 20 Hz). A mosquito produces high-frequency sound (ultrasonic), a flute produces audible sound, and a pendulum produces low-frequency but not necessarily infrasonic. Earthquakes are a natural source of infrasound.