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Sound - Terms related to Sound (Amplitude, Time Period, Frequency)

Grade 7ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Vibration: Sound is produced by the back-and-forth motion of an object, known as vibration or oscillation.

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Amplitude (AA): The maximum displacement of a vibrating body from its mean (central) position. It determines the loudness of the sound; Loudness∝A2\text{Loudness} \propto A^2. The SI unit is the metre (mm).

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Time Period (TT): The time taken by a vibrating body to complete one full oscillation. Its SI unit is the second (ss).

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Frequency (ff or ν\nu): The number of oscillations or vibrations completed by an object in one second. Its SI unit is Hertz (HzHz).

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Pitch: The shrillness or gravity of a sound. Pitch is directly proportional to the frequency; higher frequency leads to a higher pitch.

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Relationship: Frequency and Time Period are reciprocals of each other, expressed as f=1Tf = \frac{1}{T}.

📐Formulae

f=Number of VibrationsTotal Time takenf = \frac{\text{Number of Vibrations}}{\text{Total Time taken}}

T=Total Time takenNumber of VibrationsT = \frac{\text{Total Time taken}}{\text{Number of Vibrations}}

f=1Tf = \frac{1}{T}

T=1fT = \frac{1}{f}

Loudness∝(Amplitude)2\text{Loudness} \propto (\text{Amplitude})^2

💡Examples

Problem 1:

A simple pendulum makes 2020 oscillations in 4040 seconds. Calculate its frequency and time period.

Solution:

Given: Number of oscillations = 2020, Total time = 40 s40 \text{ s}. Frequency f=2040=0.5 Hzf = \frac{20}{40} = 0.5 \text{ Hz}. Time Period T=1f=10.5=2 sT = \frac{1}{f} = \frac{1}{0.5} = 2 \text{ s}.

Explanation:

Frequency is calculated by dividing the total oscillations by the time taken. The time period is the reciprocal of the frequency.

Problem 2:

The frequency of a tuning fork is 256 Hz256 \text{ Hz}. How much time does it take to complete one vibration?

Solution:

Given: f=256 Hzf = 256 \text{ Hz}. Using the formula T=1fT = \frac{1}{f}, T=1256≈0.0039 sT = \frac{1}{256} \approx 0.0039 \text{ s}.

Explanation:

To find the time for one single vibration, we calculate the Time Period (TT) using the given frequency.

Terms related to Sound (Amplitude, Time Period, Frequency) Revision - Class 7 Science ICSE