PSEB 8th Class Science Notes Chapter 13 Sound

This PSEB 8th Class Science Notes Chapter 13 Sound will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 13 Sound

→ Sound is produced by a vibrating object.

→ The maximum distance to which a vibrating body moves on either side from its mean position is called the amplitude of vibration.

→ The time taken to complete one oscillation is called the time period.

PSEB 8th Class Science Notes Chapter 13 Sound

→ The number of oscillations per second is called the frequency of oscillation.

→ Frequency is measured in hertz (Hz).

→ The larger the amplitude of vibration, the louder is the sound produced.

→ The higher the frequency of vibration, the higher is the pitch.

→ For human ears, the audible range of frequency is 20 Hz to 20000 Hz.

→ Sound needs a medium for its propagation. It cannot travel in a vacuum.

→ Light travels much faster than sound.

→ The sound may get reflected by an obstacle. The echo is produced due to reflected sound.

→ Some surfaces reflect sound better than others.

→ The pleasant effect of sound on the ear is called music while the unpleasant sound is called noise.

→ In human beings, voice is produced by the vibration of their vocal cords.

→ Amplitude: The maximum distance through which a vibrating body is displaced from its mean position.

→ Echo: The reflection of sound from an obstacle such as a building or a mountain.

→ Frequency: The number of vibrations made by a vibrating body in 1 second.

→ Hertz (Hz): The unit of frequency.

→ Larynx: Organ of voice in human beings.

→ Loudness: The property of sound which depends upon the amplitude and intensity of the vibrating body.

PSEB 8th Class Science Notes Chapter 13 Sound

→ Musical Sound: Sound which produces a pleasing effect on the ear.

→ Noise: Sound which produces a disagreeable effect on the ear.

→ Ultrasonic: Vibrations having a frequency above 20,000 Hz.

→ Vibrating Body: An object, moving to and fro about the mean position.

→ Vibrations: To and fro motion of an object.

→ Vocal Cords: Two pairs of membranous cords or folds in the larynx.

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