Maharashtra State Board Class 7 Science Sound Production of Sound / Textbook Exercises and Extra Question and Answers.
Effects of Sound Production of Sound Key Points:
Periodic Motion: A motion that repeats at fixed intervals of time is called periodic motion. Oscillatory motion is a type of periodic motion.
Oscillator: An oscillator is an object that exhibits back and forth motion around a central position. For example, a swinging pendulum is an oscillator.
Oscillation: When an oscillator completes one back-and-forth movement, it has completed one oscillation.
Sound and Vibration: Sound is produced by rhythmic vibrations of objects. The intensity of sound is proportional to the square of the amplitude of vibration.
Elasticity: Stretched rubber bands return to their original state when released due to their elastic properties. Elasticity is at work when a rubber band vibrates.
Time Period and Frequency: The time required for an oscillator to complete one oscillation is called the time period (T). Frequency (in Hertz, Hz) is the number of oscillations in one second. Frequency remains constant even if amplitude changes.
Sound Intensity and Level: Loudness is indicated by sound intensity and sound level. The decibel (dB) is used to measure sound level. Sound level can be calculated from sound intensity. A 10-fold increase in intensity results in a 10dB increase in sound level.
Ultrasonic Sound: Sound with a frequency higher than 20,000 Hz is called ultrasonic sound. Humans can’t hear it, but some animals can.
Uses of Ultrasonic Sound: Ultrasonic sound finds applications in cleaning delicate objects, medical imaging, detecting faults, radar systems, pest control, and SONAR for seabed and ship position location.
Fill in the blanks.
(a) Sound is generated by the rhythmic vibration of any object.
(b) The frequency of sound is measured in Hertz (Hz).
(c) If the amplitude of sound is decreased, its loudness also decreases.
(d) A medium is necessary for the propagation of sound.
Match the pairs. Group ‘A’ Group ‘B’
(a) Flute (3) Vibrations in the air