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📘 Study MCQs
Q1. The maximum displacement of a vibrating body from its central position is called its: Science
• Frequency
• Time period
• Amplitude
• Pitch
Answer: Amplitude
Amplitude is the measure of how far an object moves from its rest or central position during vibration. A larger amplitude means more energy is carried by the wave .
Q2. The number of oscillations or vibrations completed in one second is called the: Science
• Amplitude
• Time period
• Frequency
• Loudness
Answer: Frequency
Frequency is defined as the number of complete oscillations or vibrations that occur in one second. It determines the pitch of a sound .
Q3. The time taken to complete one full oscillation is known as the: Science
• Amplitude
• Frequency
• Time period
• Hertz
Answer: Time period
The time period is the duration required to complete one cycle of vibration. It is the reciprocal of frequency (T = 1/f) .
Q4. The SI unit of frequency is: Science
• Decibel
• Meter
• Second
• Hertz
Answer: Hertz
Frequency is measured in Hertz (Hz), named after the physicist Heinrich Hertz. One Hertz equals one oscillation per second .
Q5. If an object vibrates 50 times in one second, its frequency is: Science
• 0.02 Hz
• 50 Hz
• 100 Hz
• 25 Hz
Answer: 50 Hz
Frequency is the number of oscillations per second. Since the object completes 50 vibrations in one second, its frequency is 50 Hertz .
Q6. The property of sound that distinguishes a shrill sound from a flat sound is called: Science
• Loudness
• Pitch
• Amplitude
• Timbre
Answer: Pitch
Pitch is the characteristic of sound that helps us differentiate between a shrill (high) sound and a flat (low) sound. It depends on the frequency of vibration .
Q7. A high-pitched sound has a: Science
• Low frequency
• High frequency
• Large amplitude
• Small amplitude
Answer: High frequency
Pitch is directly related to frequency. High-frequency vibrations produce high-pitched or shrill sounds, while low-frequency vibrations produce low-pitched sounds .
Q8. The loudness of sound is determined by its: Science
• Frequency
• Time period
• Amplitude
• Speed
Answer: Amplitude
Loudness depends on the amplitude of the sound wave. A larger amplitude means the wave carries more energy, which our ears perceive as a louder sound .
Q9. The unit used to measure the loudness or sound level is the: Science
• Hertz (Hz)
• Meter (m)
• Decibel (dB)
• Second (s)
Answer: Decibel (dB)
The intensity or loudness of sound is measured in decibels (dB). It is a logarithmic unit that compares sound pressure levels .
Q10. One complete to-and-fro motion of a vibrating object is called: NCERT
• Amplitude
• Frequency
• Oscillation
• Pitch
Answer: Oscillation
An oscillation, also known as a vibration, is one complete cycle of motion—for example, the movement of a pendulum from one extreme to the other and back again .
Q11. If the time period of a wave is 0.02 seconds, what is its frequency? Science
• 0.02 Hz
• 5 Hz
• 20 Hz
• 50 Hz
Answer: 50 Hz
Frequency (f) and time period (T) are related by the formula f = 1/T. So, f = 1 / 0.02 = 50 Hz .
Q12. The pitch of a voice is high if the vocal cords are: NCERT
• Long and vibrate slowly
• Short and vibrate quickly
• Loose and thick
• Stretched loosely
Answer: Short and vibrate quickly
Short and thin vocal cords vibrate at a higher frequency. Higher frequency results in a higher pitch, which is why children and women typically have shriller voices .
Q13. The loudness of normal breathing is approximately: Science
• 10 dB
• 30 dB
• 60 dB
• 80 dB
Answer: 10 dB
The sound produced by normal, quiet breathing is very soft and measures around 10 decibels .
Q14. A soft whisper heard from a distance of 5 meters is about: Science
• 10 dB
• 30 dB
• 50 dB
• 70 dB
Answer: 30 dB
A whisper is a very faint sound. At a distance of 5 meters, a whisper typically has a loudness level of approximately 30 decibels .
Q15. The sound of busy traffic is typically around: Science
• 30 dB
• 50 dB
• 70 dB
• 100 dB
Answer: 70 dB
The constant noise from busy city traffic usually falls in the range of 70 to 80 decibels, making it much louder than normal conversation .
Q16. The noise level in an average factory is approximately: Science
• 30 dB
• 50 dB
• 80 dB
• 120 dB
Answer: 80 dB
Industrial environments with machinery typically have high noise levels. An average factory’s noise level is around 80 decibels .
Q17. Sounds with frequencies above 20,000 Hz are called: NCERT
• Infrasonic
• Ultrasonic
• Audible
• Supersonic
Answer: Ultrasonic
The human ear cannot hear frequencies above 20,000 Hz. These very high-frequency sounds are known as ultrasonic sound .
Q18. Sounds with frequencies below 20 Hz are called: NCERT
• Ultrasonic
• Audible
• Infrasonic
• Supersonic
Answer: Infrasonic
Frequencies lower than 20 Hz are below the range of human hearing and are termed infrasonic sound. Elephants use infrasound to communicate over long distances .
Q19. The range of audible frequencies for a healthy human ear is approximately: NCERT
• 1 Hz to 1000 Hz
• 20 Hz to 20,000 Hz
• 20,000 Hz to 50,000 Hz
• Above 50,000 Hz
Answer: 20 Hz to 20,000 Hz
The human auditory system is sensitive to sound waves with frequencies between 20 Hz and 20,000 Hz (20 kHz). This is called the audible range .
Q20. Which of the following animals can hear ultrasonic sounds? Science
• Elephant
• Dog
• Giraffe
• Pigeon
Answer: Dog
Dogs can hear sounds up to about 45,000 Hz, which is well into the ultrasonic range. This is why they can hear dog whistles that humans cannot .
Q21. A sound that is unwanted or unpleasant to the ear is called: NCERT
• Music
• Noise
• Pitch
• Tone
Answer: Noise
Sound can be categorized as music or noise. Noise is defined as an unwanted, unpleasant, or disruptive sound that lacks musical quality .
Q22. Which of the following sounds would be considered noise pollution? Science
• Birds chirping in a garden
• A lullaby being sung
• Sound of heavy machinery in a residential area at night
• Flowing water in a river
Answer: Sound of heavy machinery in a residential area at night
Noise pollution refers to excessive or unwanted sound in the environment that causes discomfort or harm. Loud machinery operating at night in a residential area is a clear example .
Q23. Prolonged exposure to noise pollution can cause: Science
• Improved hearing
• Hearing loss
• Increased appetite
• Better eyesight
Answer: Hearing loss
One of the primary hazards of noise pollution is noise-induced hearing loss (NIHL). Continuous exposure to high decibel levels can permanently damage the delicate hair cells in the inner ear .
Q24. The term that refers to how “shrill” or “flat” a sound is, is called: Science
• Loudness
• Pitch
• Amplitude
• Decibel
Answer: Pitch
Shrillness is another word for high pitch. A sound is considered shrill if it has a high pitch (high frequency), like a whistle, and flat if it has a low pitch, like a drum .
Q25. The frequency of a wave is 20 Hz. Its time period will be: Science
• 20 seconds
• 2 seconds
• 0.5 seconds
• 0.05 seconds
Answer: 0.05 seconds
The time period T = 1/f. Therefore, T = 1/20 = 0.05 seconds .
Q26. The loudness of sound is NOT affected by the: Science
• Amplitude of vibration
• Distance from the source
• Frequency of the sound
• Surface area of the vibrating object
Answer: Frequency of the sound
Loudness is determined by the amplitude of the wave and the energy it carries. While frequency determines pitch, it does not directly affect how loud a sound is perceived to be .
Q27. Bats navigate and find food by emitting: NCERT
• Infrasonic waves
• Ultrasonic waves
• Audible waves
• Radio waves
Answer: Ultrasonic waves
Bats produce high-frequency ultrasonic waves and listen to the echoes to locate obstacles and prey. This process is called echolocation .
Q28. Elephants can communicate over long distances using: NCERT
• Ultrasonic sounds
• Infrasonic sounds
• Audible screams
• Visual signals
Answer: Infrasonic sounds
Elephants produce very low-frequency sounds (infrasound) that can travel for several kilometers through the ground and air, allowing them to stay in touch with herds far away .
Q29. One oscillation is also known as one: NCERT
• Hertz
• Decibel
• Vibration
• Amplitude
Answer: Vibration
The terms oscillation and vibration are often used interchangeably. One oscillation is one complete vibration or cycle of motion .
Q30. Quality NCERT
• Loudness
• Pitch
Answer: Pitch
The speed or frequency of vibration (how fast the object is moving back and forth) determines the pitch of the sound produced .
Q31. Which of the following is NOT a hazard of noise pollution? Science
• Hypertension (high blood pressure)
• Insomnia (lack of sleep)
• Increased concentration
• Stress and irritability
Answer: Increased concentration
Noise pollution is known to cause stress, irritability, high blood pressure, and sleep disturbances. It distracts the mind and reduces concentration, rather than increasing it .
Q32. 1 Hertz is equal to: Science
• 1 oscillation per minute
• 10 oscillations per second
• 1 oscillation per second
• 100 oscillations per second
Answer: 1 oscillation per second
By definition, the unit Hertz (Hz) means the number of cycles or oscillations occurring each second .
Q33. If the amplitude of a wave is doubled, the loudness becomes: Science
• Half
• Double
• Four times
• Same
Answer: Four times
Loudness is proportional to the square of the amplitude of vibration. Therefore, if amplitude is doubled, loudness becomes four times greater .
Q34. The eardrum of a person can be damaged if exposed to sound louder than: Science
• 30 dB
• 60 dB
• 80 dB
• 120 dB
Answer: 120 dB
Sounds above 120 dB are at the human pain threshold and can cause immediate, permanent damage to the eardrum and inner ear structures .
Q35. Which animal can hear the highest frequency of sound (up to 150,000 Hz)? Science
• Dog
• Cat
• Dolphin
• Elephant
Answer: Dolphin
Dolphins are known to have an exceptional hearing range and can detect ultrasonic frequencies up to at least 150,000 Hz, which they use for echolocation .
Q36. The persistence of sound in a large hall due to multiple reflections is called: NCERT
• Echo
• Reverberation
• Noise
• Crest
Answer: Reverberation
Reverberation is the persistence of sound caused by multiple reflections of sound waves bouncing off the surfaces of a room or hall, making it last longer than the original sound.
Q37. Sound becomes harmful noise pollution for humans at levels above: Science
• 30 dB
• 50 dB
• 80 dB
• 100 dB
Answer: 80 dB
While sound can be annoying at lower levels, it is generally considered potentially harmful and a form of pollution when it consistently exceeds 80 dB, as this can damage hearing over time .
Q38. The quality or timbre of sound helps us to: Science
• Distinguish between a loud and soft sound
• Distinguish between a high and low pitch sound
• Distinguish between sounds of same pitch and loudness from different instruments
• Measure the frequency
Answer: Distinguish between sounds of same pitch and loudness from different instruments
Timbre (or quality) is the characteristic that allows us to tell the difference between two sounds that have the same pitch and loudness, such as a piano and a violin playing the same note .
Q39. If the time period of a vibration is 0.001 seconds, the frequency is: Science
• 10 Hz
• 100 Hz
• 1000 Hz
• 0.001 Hz
Answer: 1000 Hz
Using the formula f = 1/T, we get f = 1/0.001 = 1000 Hz, which is also called 1 kilohertz (kHz).
Q40. Which of the following is a source of noise pollution in an urban environment? Science
• School bell
• Vehicles honking in traffic
• Birds singing
• Water dripping from a tap
Answer: Vehicles honking in traffic
Unwanted and excessive sound from vehicles, especially honking in traffic, is a major contributor to noise pollution in cities and towns .
Q41. A mosquito produces sound by beating its wings at a high frequency. This sound is: NCERT
• Low pitched
• High pitched
• Very soft
• Inaudible
Answer: High pitched
A mosquito’s wings beat very fast, creating a vibration of high frequency. This high frequency translates to a high-pitched or shrill buzzing sound.
Q42. The magnitude of sound is measured in decibels. This is a measure of a sound wave’s: Science
• Frequency
• Time period
• Amplitude
• Speed
Answer: Amplitude
The decibel scale quantifies the intensity or pressure level of a sound wave, which is directly related to its amplitude .
Q43. Which of the following can be a hazard of long-term exposure to noise pollution, other than hearing loss? Science
• Improved sleep
• Lower blood pressure
• Increased stress and anxiety
• Better concentration
Answer: Increased stress and anxiety
Long-term noise pollution is linked to various non-auditory health effects, including chronic stress, anxiety, elevated blood pressure, and cardiovascular issues .
Q44. The frequency of a sound wave is 10,000 Hz. This sound is: Science
• Infrasonic
• Audible
• Ultrasonic
• Supersonic
Answer: Audible
Since the human audible range is 20 Hz to 20,000 Hz, a frequency of 10,000 Hz falls well within this range and is therefore clearly audible.
Q45. A complete back-and-forth movement of a pendulum from its starting point is: NCERT
• One frequency
• One oscillation
• One hertz
• One amplitude
Answer: One oscillation
When a pendulum bob moves from its starting position, to one end, to the other end, and back to the start, it has completed one full oscillation .
Q46. The maximum sound level that a human ear can tolerate without feeling pain is about: Science
• 60 dB
• 80 dB
• 100 dB
• 120 dB
Answer: 120 dB
The threshold of pain for the human ear is typically around 120 dB. Sounds above this level can cause immediate pain and potential hearing damage .
Q47. The voice of a lion is low-pitched because its vocal cords are: NCERT
• Short and vibrate quickly
• Long and vibrate slowly
• Thin and tight
• Not present
Answer: Long and vibrate slowly
A large animal like a lion has long vocal cords. These longer cords vibrate with a lower frequency, producing a low-pitched or flat roar .
Q48. Unwanted sound in the environment that causes health issues is called: NCERT
• Music
• Noise pollution
• Ultrasound
• Frequency
Answer: Noise pollution
When unwanted or excessive sound disrupts the natural balance and causes health problems or annoyance in human and animal life, it is termed noise pollution .
Q49. The loudness of a sound of a source decreases when we move away from it because: Science
• Frequency decreases
• Amplitude decreases
• Pitch decreases
• Speed decreases
Answer: Amplitude decreases
As we move away from a sound source, the energy of the sound wave spreads out over a larger area. This results in a decrease in the amplitude of the wave, making it sound quieter .
Q50. Infrasonic sound can be produced by: Science
• A mosquito
• A flute
• A pendulum
• An earthquake
Answer: An earthquake
Natural disasters like earthquakes, volcanic eruptions, and avalanches produce very low-frequency vibrations that are below 20 Hz, known as infrasonic waves .