Class 9 Physics Sound Wavelength Frequency Time Period

Wavelength, Frequency, Time Period

  • Wavelength: The distance between 2 consecutive crest or troughs is called Wavelength. It is represented by the symbol  λ(lamda). Unit is m.


  • Time Period: The time taken for one complete oscillation in the density of the medium is called the Time Period of the wave. It can also be defined as the time taken by 2 consecutive compressions or rarefactions to cross a fixed point. It is represented by the symbol T. Its unit is in seconds.


  • Frequency : The number of oscillations per unit time is called the Frequency of the sound wave. The number of compressions or rarefactions that cross a given point in per unit time is the frequency of the wave. It is denoted by μ and is unit is Hz (Hertz).

A sound of a single frequency is called Tone. A sound which is a mixture of different frequencies is called Note and is very pleasant to listen to.


Frequency   =    No of oscillations  
                            Time (in seconds)

 μ    =   1/T


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