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Find Frequency of Wave

May 11, 2013

Introduction to find frequency of wave

The frequency of a wave is equal to the number of vibrations or oscillation the particles of the medium execute per second during the wave propagation. The energy of the wave is associated with its frequency. The following is the formula to calculate the frequency of a wave when its wavelength and speed in a medium is given. There is an inverse relation between the frequency and the wavelength, higher the wavelength lower is the frequency. When a light pass from a medium to another medium the parameters like velocity and the wavelength changes but the frequency does not. The energy of a wave is directly related to its frequency.


Velocity of wave = frequency * wavelength

Therefore to calculate the frequency

                        Frequency =   Velocity /wavelength

                                 F= V/λ

V=    Velocity (m/sec)

λ = Wavelength (meter)

The SI unit of frequency is Hertz or cycle per second or Sec-1

Find frequency of wave

Question: Find the frequency of a sound wave which travels with the speed of 332 m / sec in air. The wavelength of the wave is 300 cm.

Solution:  λ = 300 cm = 3 meter

V= 332 m/sec

F= V/λ

                      = 332/3 = 110.67 Hertz

Question: calculate the frequency of red light the wave length of red light is approximately 7800 Ao .

Solution : the speed of light wave C = 3.0*108 meter/second

1Ao =10-10 meter therefore 7800 Ao =7800* 10-10

                                                                                = 7.8*10-7 meter

F= V/λ

                                                              = 3.0*108/7.8*10-7

= 3.84 *1015 Hertz

The relation between the time period and the frequency of oscillation of a wave is given as

Frequency = 1/ Time period

 Question: find the frequency of the wave when the period of oscillation of the medium of the particle is 2 second.

Solution:   f =1/T = ½ = 0.5 sec-1 or hertz

The frequency of a wave is related to the energy of the wave higher the frequency higher the energy it carries. There is more type of frequency in the Physics; they are angular frequency the angular frequency is given by the formula

ώ= 2Лf

ώ = angular frequency (radian /sec)

f = frequency of the oscillation or rotation


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