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What is the frequency of a wave?

Courtney Durso, David Wood
  • Author
    Courtney Durso

    Courtney is a certified Biology and Physics teacher from Pennsylvania. She has an undergraduate degree from Penn State University in Animal Bioscience, a master's degree from Arcadia University in Secondary Education, and is currently pursuing her second master's degree in Curriculum and Instruction from Gannon University. Courtney has ten years of instructional experience in a classroom.

  • Instructor
    David Wood

    David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

Explore what the frequency of a wave is. Discover the formula and units of the frequency. Understand how the frequency is related to the energy of a wave. Updated: 05/17/2022

What is the Frequency of a Wave

A wave is a type of disturbance that moves. Many waves must travel through a medium such as air or water; these waves are known as mechanical waves. Other types of waves, electromagnetic waves, are capable of traveling through mediums as well as through a vacuum. Waves have several distinct properties that help describe their motion and energy including frequency and wavelength. As to what frequency is, it is defined, in a general sense, as to how often something occurs, or basically, how often a wave occurs. The frequency of a wave is the number of waves that pass a point in a certain period of time. Frequency can also be described as the number of waves that pass a point in one second. Waves that are moving more quickly will have a higher frequency than waves that are moving slowly.

Definition of Frequency

Have you ever wondered why the sky is blue? Or, more to the point, why anything has a color in the first place? Your father's voice might have been deep, and your mother's voice not so deep. Whether it's colors, or the notes on a piano, these things are all explained by frequency.

Frequency is a property of a wave. We are surrounded by waves every day. Light is an electromagnetic wave, and the sound of the fan in your computer is a sound wave. A wave is a vibration that carries energy with it. The frequency of a wave is the number of waves that pass by each second, and is measured in Hertz (Hz). For example, a sound wave might have a frequency of 450 Hz.

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  • 0:47 Frequency in Light
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What is Frequency Formula

Wave frequency can be calculated using the frequency formula. The frequency formula works by dividing the wave speed (v) by the wavelength ({eq}\lambda {/eq}). Wavelength is the distance from the top of one wave to the top of the next wave; it is essentially the length of one full wave cycle. The unit for wavelength is meters.


Frequency ={eq}\frac{v}{\lambda} {/eq}


For example, if a wave is traveling 3 m/s and it has a 2-meter wavelength, you would set the equation up as follows:

{eq}\frac{3 m/s}{2 m} = 1.5 Hz {/eq}

Frequency can also be calculated by dividing 1 by the period (T) of the wave.


{eq}F=\frac{1}{T} {/eq}


The period of the wave is the time it takes the wave to complete one full cycle. The unit for the period is seconds.

The following is an example of using the period to solve for frequency. If it takes a wave 30 seconds to complete one full cycle, then the frequency is 0.03 Hz.


{eq}0.03 Hz = \frac{1}{30} {/eq}


Units of Frequency

The frequency unit is Hertz (Hz). The unit is named Hertz because it is named after Heinrich Hertz, a German physicist who discovered radio waves and confirmed the existence of electromagnetic waves. A hertz is equal to one wave cycle per second.


Heinrich Hertz

Photograph of Heinrich Hertz


Examples of Frequency

Different types of waves have different frequencies. Higher frequency waves have shorter wavelengths while lower frequency waves have longer wavelengths. Frequency also corresponds to energy: high-frequency waves have higher energy, and low-frequency waves have low energy. The frequency of a wave determines how it is perceived: whether the wave is heard, visible, causes damage, etc. Waves with extremely high frequency, such as gamma rays, cause tremendous damage but are unseen and unheard because the wavelength of these waves is small.


Wave frequencies

Chart containing common wave frequencies


Frequency of Light

Visible light waves range from 430 trillion Hz waves, which is red light, to 750 trillion Hz waves, which is violet light. The frequency of the light wave determines what color the human eye perceives. Lower energy waves, with relatively lower frequencies, resulting in "warmer" colors such as red, orange, and yellow. As wave energy increases, so does the frequency. These relatively higher frequency waves result in "cooler" colors such as green, blue, and violet. Visible light progresses from low frequency to high frequency in the same order as prismatic color: red, orange, yellow, green, blue, indigo, and violet. The human eye is capable of seeing waves with frequencies between 405 trillion Hz and 790 trillion Hz. Waves that have higher frequencies than spectral light waves include infrared waves, x-rays, and gamma rays.

Frequency in Light

Light is an electromagnetic wave; it is a vibration in electric and magnetic fields. Because of this, it can travel through the vacuum of space, and thank goodness for that! If that wasn't the case, we would get no heat from the sun, and life on Earth would be impossible.

There are more wavelengths than we see with human eyes. A full continuous spectrum would include radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma rays. The diagram on your screen shows the full electromagnetic spectrum and everything it contains.

The Electromagnetic Spectrum

Frequency tells you the color of light. High frequency light waves are at the blue end of the spectrum, and low frequency light waves are at the red end of the spectrum. Our eyes detect the frequency of the light, and our brains interpret it as color. Some philosophers have thought that perhaps color itself only exists in our brains; unfortunately, we have no way of knowing for sure.

Frequency in Sound

Sound waves are wave vibrations in the air. When you slap your hand on the desk, it causes the desk to vibrate, which causes the air to vibrate. The air particles hit each other until they reach your ear, making your ear drum vibrate. Your ear drum then sends a signal to your brain. It's your brain that interprets these vibrations.

Frequency tells you the pitch of sound. High frequency sound is high pitched, and low frequency sound is low pitched. Again, one might ask the question of whether pitch is just the way our brain interprets the waves, or if it's a real thing.

Every musical note you could play on the piano is a different frequency. In fact, if you've ever used a tuning fork, you might notice that the frequency of the note (in Hertz) is stamped on it for reference. Our ears can hear frequencies between 20 Hz and 20,000 Hz.

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Video Transcript

Definition of Frequency

Have you ever wondered why the sky is blue? Or, more to the point, why anything has a color in the first place? Your father's voice might have been deep, and your mother's voice not so deep. Whether it's colors, or the notes on a piano, these things are all explained by frequency.

Frequency is a property of a wave. We are surrounded by waves every day. Light is an electromagnetic wave, and the sound of the fan in your computer is a sound wave. A wave is a vibration that carries energy with it. The frequency of a wave is the number of waves that pass by each second, and is measured in Hertz (Hz). For example, a sound wave might have a frequency of 450 Hz.

Frequency in Light

Light is an electromagnetic wave; it is a vibration in electric and magnetic fields. Because of this, it can travel through the vacuum of space, and thank goodness for that! If that wasn't the case, we would get no heat from the sun, and life on Earth would be impossible.

There are more wavelengths than we see with human eyes. A full continuous spectrum would include radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma rays. The diagram on your screen shows the full electromagnetic spectrum and everything it contains.

The Electromagnetic Spectrum

Frequency tells you the color of light. High frequency light waves are at the blue end of the spectrum, and low frequency light waves are at the red end of the spectrum. Our eyes detect the frequency of the light, and our brains interpret it as color. Some philosophers have thought that perhaps color itself only exists in our brains; unfortunately, we have no way of knowing for sure.

Frequency in Sound

Sound waves are wave vibrations in the air. When you slap your hand on the desk, it causes the desk to vibrate, which causes the air to vibrate. The air particles hit each other until they reach your ear, making your ear drum vibrate. Your ear drum then sends a signal to your brain. It's your brain that interprets these vibrations.

Frequency tells you the pitch of sound. High frequency sound is high pitched, and low frequency sound is low pitched. Again, one might ask the question of whether pitch is just the way our brain interprets the waves, or if it's a real thing.

Every musical note you could play on the piano is a different frequency. In fact, if you've ever used a tuning fork, you might notice that the frequency of the note (in Hertz) is stamped on it for reference. Our ears can hear frequencies between 20 Hz and 20,000 Hz.

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Frequently Asked Questions

What is frequency and what is its unit?

Frequency is defined as the number of waves that pass a certain point in one second. The unit for frequency is the hertz (Hz).

What is meant by frequency in sound?

Frequency in sound refers to the number of mechanical sound waves that pass a certain point in one second. Higher frequency sound waves produce higher-pitched sounds.

What is the best definition of frequency?

The frequency of waves is how many waves pass a given point in a specific unit of time. Frequency is directly proportional to the energy. The higher the frequency, the higher the energy.

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