MCQ (Solution) - Sound | Science Class 8 PDF Download

Q1: What is the primary cause of sound production?
(a)  Heat
(b) Light
(c) Vibration
(d) Electricity

Correct Answer is Option (c)

• The primary cause of sound production is vibration. 
• When an object vibrates, it causes the air particles around it to move back and forth, creating sound waves that travel to our ears. 
• For example, when you pluck a guitar string, it vibrates and produces sound. 
• Without vibration, no sound can be created. Vibration of Air Particles

Q2: What is the role of the larynx in sound production by humans? 
(a) Filtering sound 
(b)  Controlling amplitude 
(c)  Producing sound
(d) Enhancing pitch 

Correct Answer is Option (c)

• The larynx, also known as the voice box, plays a crucial role in sound production in humans. 
• It contains the vocal cords, which vibrate when air passes through them, producing sound. 
• The tension and length of the vocal cords determine the pitch and tone of the sound. 
• Hence, the primary function of the larynx is to produce sound.

 

Larynx

Q3: In which medium does sound travel the fastest? 
(a)  Solids 
(b) Liquids 
(c) Gases 
(d) Vacuum 

Correct Answer is Option (a)

• Sound travels the fastest in solids because the particles in solids are packed very closely together. 
• This makes it easier for vibrations (which create sound) to pass from one particle to the next. 
• In comparison, particles in liquids and gases are farther apart, so sound travels more slowly. 
• In a vacuum, there are no particles, so sound cannot travel at all.

Q4: What characteristic determines the loudness of a sound wave? 
(a) Amplitude 
(b) Frequency 
(c) Time period 
(d)  Propagation speed 

Correct Answer is Option (a)

• The loudness of a sound wave depends on its amplitude. 
• Amplitude is how big the wave is or how far the particles of the medium move from their resting position. 
• A larger amplitude means the sound is louder, while a smaller amplitude means the sound is softer.  

Q5: What is the unit of frequency? 
(a) Watts 
(b) Hertz 
(c) Decibels 
(d) Newton 

Correct Answer is Option (b)

• The unit used to measure frequency is called hertz (Hz).
• One hertz means one cycle happening in one second.
• It is named after Heinrich Hertz, a German scientist who greatly advanced the study of electromagnetism and waves.

Q6:What is the range of audible sound for humans? 
(a)  5 Hz to 50,000 Hz 
(b) 10 Hz to 100,000 Hz 
(c) 20 Hz to 20,000 Hz 
(d) 15 Hz to 30,000 Hz 

Correct Answer is Option (c)

• The range of audible sound for humans typically falls between 20 hertz (Hz) and 20,000 Hz.

• The lower limit of 20 Hz represents the lower threshold of human hearing, while the upper limit of 20,000 Hz represents the higher threshold.

Q7: The minimum distance from a sound-reflecting surface required to hear an echo is:
(a) 10 meters
(b) 17 meters
(c) 20 meters
(d) 34 meters

Correct Answer is Option (b)

• An echo is heard when sound reflects off a surface and comes back to our ears. 
• For the echo to be clear and distinct, the reflected sound must take enough time to reach our ears after the original sound. 
• This happens only if the surface is at least 17 meters away. 
• If the distance is less, the reflected sound mixes with the original sound, and no distinct echo is heard.

Q8: What health problems can be caused by noise pollution? 
(a) Improved sleep 
(b) Enhanced concentration 
(c) Hypertension 
(d)  Increased hearing ability 

Correct Answer is Option (c)

• Noise pollution has been associated with an increased risk of hypertension, and several mechanisms may contribute to this relationship. 
• Prolonged exposure to high levels of noise can activate the body's stress response, leading to physiological changes that may contribute to hypertension.
  Hypertension Disorder

Q9:  Infrasound can be produced by –
(a) whales
(b) dolphins
(c) bats
(d) porpoise

Correct Answer is Option (a)

• Infrasound refers to sound waves with frequencies below the range of human hearing, typically less than 20 Hz. 
• Whales are known to produce infrasound for communication over long distances in the ocean. 
• Other animals, like dolphins, bats, and porpoises, use high-frequency sounds (ultrasound) for echolocation, which is the opposite of infrasound. 
• Hence, the correct answer is whales.

Q10: What does the frequency of a sound wave determine? 
(a)  Loudness 
(b) Pitch
(c) Time period 
(d) Propagation speed 

Correct Answer is Option (a)

• The frequency of a sound wave determines its pitch. 
• Frequency is the number of vibrations or waves produced in one second. 
• A higher frequency means a higher pitch (like the sound of a whistle), and a lower frequency means a lower pitch (like the sound of a drum).
• So, the pitch of a sound depends on how fast the vibrations are occurring.