Learn Science Sound, Class 8 Science Sound Exercise, Free Online Sound Lessons

Class 8 Science Study Material

An Educational platform for Preparation and Practice Class 8. Kidsfront provide unique pattern of learning Science with free online comprehensive study material in the form of QUESTION & ANSWER for each Chapter of Science for Class 8. This study material help Class 8, Science students in learning every aspect of Sound. Students can understand Sound concept easily and consolidate their learning by doing Online Practice Tests on Science,Sound chapter repeatedly till they excel in Class 8, Sound. Free ONLINE PRACTICE TESTS on Class 8, Sound comprise of Hundreds of Questions on Sound, prepared by the highly professionals team. Every repeat test of Sound will have new set of questions and help students to prepare themselves for exams by doing unlimited Online Test exercise on Sound. Attempt ONLINE TEST on Class 8,Science,Sound in Academics section after completing this Sound Question Answer Exercise.

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Topic wise:Sound preparation in the form of QUESTION & ANSWER.
Evaluate preparation by doing ONLINE TEST of Class 8, Science,Sound.
Review performance in PRACTICE TEST and do further learning on weak areas.
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Evaluate your progress by doing ONLINE MOCK TEST of Class 8, Science, All TOPICS.

Sound

The loudness of sound is measured with a

a) Vernier scale.
b) Decibel meter.
c) Meter scale.
d) Screw gauge.

✔Answer

✔Solution

Correct Answer Is : Decibel meter.

Solution Is : Loudness of sound is measured in decibels. Decibel meter is also known as `sound level meter` or `dB meter`. Decibel meter is an instrument used to measure the noise and sound levels in a specified manner, which is calibrated in decibels.

Galton`s whistle is

a) An ultrasonic device to trained dogs
b) Used to produce soft melodious sound.
c) An infrasonic device to trained dogs
d) Used to produce noise.

✔Answer

✔Solution

Correct Answer Is : An ultrasonic device to trained dogs

Solution Is : Galton`s whistle is made to produce sounds of frequency above 20 kHz which are easily heard by dogs but they are not audible to human ear. Ultrasound has frequency range above 20,000 Hz. Hence, Galton`s whistle is used as an ultrasonic device to trained dogs.

For an echo to be heard, the distance between the source and the reflecting surface must be approximately more than

a) 17 m.
b) 17 cm.
c) 10 m.
d) 10 cm.

✔Answer

✔Solution

Correct Answer Is : 17 m.

Solution Is : Echo is a reflected sound when the reflecting surface is at a distance of more than approximately 17 m from the source. Surfaces which are near by or far away from the source, reflects sound. But we hear the echo from the surface which is far away. This is due to the reason that our ears are not able to distinguish the echo as a separate sound if it reaches our ear very quickly.?

If a pendulum vibrates 50 oscillations in 5 seconds, its frequency is

a) 5 Hz.
b) 10 Hz
c) 15 Hz.
d) 50 Hz.

✔Answer

✔Solution

Correct Answer Is : 10 Hz

Solution Is : Frequency is the number of oscillations in 1 second. Number of oscillations made by the pendulum in 5 sec = 50 Number of oscillation made by the pendulum in 1 sec = 50/ 5 = 10 So, 10 oscillations are made by the pendulum in 1 second, i.e., its frequency = 10 Hz.

Sound can travel through

a) Gases only.
b) Solids only.
c) Liquids only.
d) Any material medium which includes solids, liquids and gases.

✔Answer

✔Solution

Correct Answer Is : Any material medium which includes solids, liquids and gases.

Solution Is : Sound needs a material medium for its propagation. Therefore, it can travel through solids, liquids and gases but can`t travel vacuum

The amplitude of sound changes suddenly in case of a

a) Soft sound like musical sound
b) Sound produced by guitar
c) Noise.
d) Sound produced by veena.

✔Answer

✔Solution

Correct Answer Is : Noise.

Solution Is : Musical sound is produced by regular and periodic vibrations in a material. But noise is produced by irregular vibrations in a body. Thus, the amplitude of vibrations in case of a noise, changes suddenly.

The number of oscillations per second is called the

a) Time period.
b) Amplitude.
c) Frequency.
d) Displacement.

✔Answer

✔Solution

Correct Answer Is : Frequency.

Solution Is : Frequency means the number of times a thing happens or appears. In sound, the number of times, oscillations take place in a given time is `frequency`. Frequency is defined as the number of oscillations per unit time.

Loudness of sound depends upon the

a) Pitch.
b) Frequency.
c) Time period.
d) Amplitude.

✔Answer

✔Solution

Correct Answer Is : Amplitude.

Solution Is : The amplitude of vibration producing sound determines the loudness of a sound. Loudness of sound depends upon the square of the amplitude of vibration producing sound. The unit of loudness is called decibel (dB).

Sound is produced when objects

a) Rotate
b) Vibrate.
c) Circulate.
d) Move linearly.

✔Answer

✔Solution

Correct Answer Is : Vibrate.

Solution Is : Vibrations produce sound as they disturb the air. When a body moves to and fro or back and forth, it produces vibrations

The section of human throat which produces voice is the

a) Wind pipe.
b) Voice box.
c) Throat.
d) Lungs.

✔Answer

✔Solution

Correct Answer Is : Voice box.

Solution Is : There are two vocal chords which are stretched across the voice box in our throat in such a way that a narrow slit is left between them for the air to pass through it. When the air is forced by the lungs through the narrow slit, the vocal cords vibrate and produces sound.

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Class 8 Science Study Material

Sound

The loudness of sound is measured with a

Correct Answer Is : Decibel meter.

Solution Is : Loudness of sound is measured in decibels. Decibel meter is also known as `sound level meter` or `dB meter`. Decibel meter is an instrument used to measure the noise and sound levels in a specified manner, which is calibrated in decibels.

Galton`s whistle is

Correct Answer Is : An ultrasonic device to trained dogs

Solution Is : Galton`s whistle is made to produce sounds of frequency above 20 kHz which are easily heard by dogs but they are not audible to human ear. Ultrasound has frequency range above 20,000 Hz. Hence, Galton`s whistle is used as an ultrasonic device to trained dogs.

For an echo to be heard, the distance between the source and the reflecting surface must be approximately more than

Correct Answer Is : 17 m.

If a pendulum vibrates 50 oscillations in 5 seconds, its frequency is

Correct Answer Is : 10 Hz

Solution Is : Frequency is the number of oscillations in 1 second. Number of oscillations made by the pendulum in 5 sec = 50 Number of oscillation made by the pendulum in 1 sec = 50/ 5 = 10 So, 10 oscillations are made by the pendulum in 1 second, i.e., its frequency = 10 Hz.

Sound can travel through

Correct Answer Is : Any material medium which includes solids, liquids and gases.

Solution Is : Sound needs a material medium for its propagation. Therefore, it can travel through solids, liquids and gases but can`t travel vacuum

The amplitude of sound changes suddenly in case of a

Correct Answer Is : Noise.

Solution Is : Musical sound is produced by regular and periodic vibrations in a material. But noise is produced by irregular vibrations in a body. Thus, the amplitude of vibrations in case of a noise, changes suddenly.

The number of oscillations per second is called the

Correct Answer Is : Frequency.

Solution Is : Frequency means the number of times a thing happens or appears. In sound, the number of times, oscillations take place in a given time is `frequency`. Frequency is defined as the number of oscillations per unit time.

Loudness of sound depends upon the

Correct Answer Is : Amplitude.

Solution Is : The amplitude of vibration producing sound determines the loudness of a sound. Loudness of sound depends upon the square of the amplitude of vibration producing sound. The unit of loudness is called decibel (dB).

Sound is produced when objects

Correct Answer Is : Vibrate.

Solution Is : Vibrations produce sound as they disturb the air. When a body moves to and fro or back and forth, it produces vibrations

The section of human throat which produces voice is the

Correct Answer Is : Voice box.

Solution Is : There are two vocal chords which are stretched across the voice box in our throat in such a way that a narrow slit is left between them for the air to pass through it. When the air is forced by the lungs through the narrow slit, the vocal cords vibrate and produces sound.

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