Content

• To step
• Method 1 of 4: Frequency and wavelength
• Method 2 of 4: Frequency of electromagnetic waves in a vacuum
• Method 3 of 4: Calculate frequency if the time or period is given
• Method 4 of 4: Calculate the frequency if the corner frequency is given
• Necessities

Frequency or wave frequency measures the number of vibrations within a certain time. There are a number of different ways to calculate the frequency, depending on the data available. Keep reading to learn some of the most common and useful methods.

To step

Method 1 of 4: Frequency and wavelength

1. Learn the formula. You write the formula for frequency, at a given wavelength and wave speed, as: f = v / λ
   • This formula states f for the frequency, v for the wave speed and λ for the wavelength.
   • Example: A certain sound wave travels through the air with a wavelength of 322 nm and a speed of 320 m / s. What is the frequency of this sound wave?
2. Convert the wavelength to meters, if necessary. If the wavelength is given in nanometers, then you will have to convert this value to meters by dividing it by the number of nanometers in 1 meter.
   • Note that when working with extremely small numbers or extremely large numbers, it is usually easier to put the values ​​in scientific notation. The values ​​in the following example will be given in both scientific and decimal form, but if you are doing homework assignments, you will usually use scientific notation.
   • Example: λ = 322 nm
     • 322 nm x (1 m / 10 ^ 9 nm) = 3.22 x 10 ^ -7 m = 0.000000322 m
3. Divide the speed by the wavelength. Share the speed of the wave, v, converted to meters by wavelength, λ, to the frequency, f, to be able to determine.
   • Example: f = v / λ = 320 / 0.000000322 = 993788819.88 = 9.94 x 10 ^ 8
4. Write down your answer. After completing the previous step, you have calculated the wave frequency. Write your answer in Hertz, Hz, the unit of frequency.
   • Example: The frequency of this wave is 9.94 x 10 ^ 8 Hz.

Method 2 of 4: Frequency of electromagnetic waves in a vacuum

1. The formula for calculating the wave frequency. The formula for the frequency of a wave in a vacuum is almost identical to that of a wave outside a vacuum. However, because there are no outside influences on the speed of the wave, you use the speed of light which is equal to the speed of electromagnetic waves. The formula then reads as follows: f = c / λ
   • In this formula f the frequency, c the speed of light, and λ the wavelength.
   • Example: a certain electromagnetic radiation wave has a wavelength of 573 nm in a vacuum. What is the frequency of this electromagnetic wave?
2. Convert the wavelength to meters, if necessary. If the wavelength is given in meters in the statement, you do not have to do anything. However, if the wavelength is given in micrometers, you will have to convert this to meters by dividing this value by the number of micrometers in a few meters.
   • Note that when dealing with very large or very small numbers, it is usually better to use scientific notation. The values ​​in the following example will be given in both scientific and decimal form, but if you are doing homework assignments, you will usually use scientific notation.
   • Example: λ = 573 nm
     • 573 nm x (1 m / 10 ^ 9 nm) = 5.73 x 10 ^ -7 m = 0.000000573
3. Divide the speed of light by the wavelength. The speed of light is a constant, viz. 3.00 x 10 ^ 8 m / s. Divide this value by the wavelength in meters.
   • Example: f = C / λ = 3.00 x 10 ^ 8 / 5.73 x 10 ^ -7 = 5.24 x 10 ^ 14
4. Write down your answer. This is the wave frequency. Write your answer in Hertz, Hz, the unit of frequency.
   • Example: The frequency of this wave is 5.24 x 10 ^ 14 Hz.

Method 3 of 4: Calculate frequency if the time or period is given

1. Learn the formula. Frequency and time for a full wave motion are inversely related. The formula for the wave frequency for a given duration of a wave is as follows: f = 1 / T
   • In this formula f the frequency and T. the period (the time to go through a full wave motion.
   • Example A: The period of a wave is 0.32 seconds. What is the frequency of this wave?
   • Example B: In 0.57 seconds a certain wave goes through 15 oscillations (15 waves). What is the frequency of this wave?
2. Divide the number of oscillations by the period. Usually it is given what the period of a wave is, so you just 1 divide by the duration of a period T.. If instead you were given a duration for a number of oscillations, then you will have to divide this total by the duration of 1 oscillation (a period).
   • Example A: f = 1 / T = 1 / 0.32 = 3.125
   • Example B: f = 1 / T = 15 / 0.57 = 26,316
3. Write down your answer. With this you have calculated the wave frequency. Write your answer in Hertz, Hz, the unit of frequency.
   • Example A: The frequency of this wave is 3.125 Hz.
   • Example B: The frequency of this wave is 26,316 Hz.

Method 4 of 4: Calculate the frequency if the corner frequency is given

1. Learn the formula. If the angular frequency of a wave is given but the regular wave frequency is not, then you write the formula for the wave frequency as follows: f = ω / (2π)
   • In this formula f the wave frequency and ω the corner frequency. The symbol π stands for pi, a mathematical constant.
   • Example: a particular wave is rotating at an angular frequency of 7.17 radians per second. What is the frequency of that wave?
2. Multiply pi by 2. To find the denominator of the equation, you will have to multiply pi by 2.
   • Example: 2 * π = 2 * 3.14 = 6.28
3. Divide the corner frequency by 2 * pi. Divide the angular frequency, given in radians per second, by 6.28, or 2π.
   • Example: f = ω / (2π) = 7.17 / (2 * 3.14) = 7.17 / 6.28 = 1.14
4. Write down your answer. With this calculation you have found the wave frequency. Write your answer in Hertz, Hz, the unit of frequency.
   • Example: The frequency of this wave is 1.14 Hz.

Necessities

• Calculator
• Pencil
• Paper