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# Frequency and Wavelength

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Last updated date: 05th Aug 2024
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## Introduction

We have heard of waves in our everyday lives like water waves and sound waves. On this page, we will learn what a Wave is and its primary characteristics.

We can define a Wave as a continuous and recurring disturbance of a medium.

In our world, we observe various phenomena like throwing a stone in the water and seeing ripples, plucking the strings of a guitar, an oscillating string of thread, earthquake waves, and tsunami waves.

A wave needs a medium to propagate. Without this medium, a wave would not be able to travel. The medium itself does not move, but if we look at it as an interlinked series of several particles, we can say that when a wave interacts with one particle. It allows the wave to pass through the disturbance to the interacting particles. For example, a spring coil has a medium of a metal spring, just like in the case of a sound wave, the air through which that wave travels is its medium

Waves only transport energy and do not matter. Suppose there is a disturbance in the medium which is transporting the wave. In that case, the particles temporarily become displaced from their position and only get back to their original position if a restoring force brings them back there.

### Types of Waves

We can categorize waves into three types. This depends on how the particles are directed and propagated through that wave:

Transverse Wave: When the particle movement is perpendicular to the energy's direction of the movement in the medium. Example: Wave of a rope.

Longitudinal Wave: When the particle movement is parallel to the energy's direction of the movement in the medium. Example: Sound moving through the air and forming a pattern.

Surface Waves: When the particle movement occurs along the energy's direction of the movement in the medium in a circular motion. Example: Seismic Waves, Electromagnetic Waves

Before getting into Frequency and Wavelength, let us know some more essential terms.

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Crest: A crest is the highest point of the wave.

Trough: The trough is the lowest point in a wave.

Wave Height: Wave Height is the vertical distance we can observe between the crest and the trough near it.

Amplitude: An amplitude is half of the height of a wave. We can define amplitude as the measure of disturbance in a substance from the equilibrium position.

### Frequency

The term frequency means the number of times a particle vibrates when the sound wave passes through a medium. We measure frequency as the total number of vibrations in a unit of time.

For example, suppose a longitude wave vibrates about 10000 vibrations in 5 seconds. In that case, its frequency will be 2000 vibrations per second. The unit for frequency is Hertz.

1 Hertz = 1 Vibration/Second

When a sound wave travels through a medium, each particle in that medium vibrates at the same frequency. This happens because each particle vibrates due to its neighboring particle. Since only energy gets transferred, they vibrate at the same frequency as the previous particles.

The speed of a wave also depends on the medium through which it travels. For example, the speed of light is lesser in a medium when it travels through a vacuum instead of air. This also tells us that this same frequency corresponds to a shorter wavelength in any medium than the vacuum.

### Wavelength

Wavelength can be defined as the distance between the two consecutive crests or troughs in a curve. In a high-frequency wave, the distance between the crests and troughs is less than in a low-frequency wave and vice-versa.

Frequency is inversely related to Wavelength.

We measure Wavelength in nanometers, denoting it by the Greek Symbol Lambda (λ).

We more commonly apply the concept of a wavelength to waves of a sinusoidal pattern.

Sinusoidal Pattern is also commonly known as a Sine Wave, which describes a smooth periodic oscillation. A Sine wave is continuous, and we name it after the sine function.

In a linear system, we observe that the sinusoid is one of the simplest forms without disturbing its shape.

Mediums like Light, Water, and Sound all travel as waves. The equation we use to donate their motion is the same, which is:

F = c/λ

Here, we see that F is the wave's frequency, whereas c is the speed, and Lambda is the Wavelength.

We can find Electromagnetic Waves in mediums like Light. We can describe them by their frequency, wavelengths, and energy. These three properties of the electromagnetic wave relate to Light and one another.

All lights travel at the same speed regardless of their color. However, if their wavelengths are different, they can turn into different colors. We can often see these lights separate into different colors in a prism. Red has the lowest frequency and the longest Wavelength in that spectrum that we produce. In contrast, on the other end, violet has the highest frequency but the lowest Wavelength.

This tells us that the higher the wave's energy, the higher is the frequency and the longest Wavelength. In the same way, colors of a short wavelength also have a high frequency. They are more vibrant than the colors with a longer wavelength and lower frequency.

## FAQs on Frequency and Wavelength

1. How do waves transport energy?

Waves can carry energy with them through a medium. A wave medium is a substance that carries a wave from one location to another.

One thing to note is that a directionally proportional restoring force always resists any wave displacement.

This humongous task of producing a giant wave that will produce amplitude through the medium requires a lot of displacement and force. This results in the production of more wave energy.

Hence, we can say that this is how waves transport energy as it increases with the help of a dynamic amplitude.

2. How can we differentiate between a Transverse Wave and a Longitudinal Wave?

There are several differences between a longitudinal wave and a transverse wave:

• Movement of the Medium: In Longitudinal Waves, the medium moves in the same path as the wave. On the other hand,  Transverse Waves have a medium that moves perpendicular to the wave's direction.

• Dimension: Longitudinal Waves act in one dimension, whereas Transverse waves occur in two dimensions.

• Alignment: Longitudinal Waves cannot be aligned or polarized, whereas Transverse Waves can be aligned and polarized.

• Production: Longitudinal Waves can be produced in any medium, whether gaseous, solid, or liquid. On the other hand, transverse Waves can only be produced in a solid and a liquid's surface.

• Examples: Earthquake P wave is longitudinal, whereas Earthquake S waves are Transverse.

• Composition: Longitudinal Waves are made up of compressions and rarefactions. Longitudinal Waves are made up of crests and troughs.

3. How do we communicate through waves?

As waves can travel effortlessly in the medium of air and do not damage our senses if we absorb these waves. That is why we use them to transmit messages to each other and create a communication space.

A well-known example of this is Radio Waves that we humans use heavily for communication in television and radio. Radio Wave transmission is based on a simple principle, where a transmitter encodes/modulates a message by varying the amplitude of the wave, and on the other end, a receiver is tuned to that same length wave and takes that sent signal and then decodes it informs that we desire, like images, data, and sounds.

4. What are some essential terms we should know in this concept?

We should be aware of some essential terms when talking about waves and frequencies. These terms are:

• Periodic Wave: A wave that repeats simultaneously over space and time. They are also known as continuous waves.

• Wavelength: This is the difference between the neighboring maximum and minimum parts of a wave. We donate it by the symbol λ.

• Crest: It is the highest point on a transverse wave. We also call it a Peak.

• Trough: Lowest Points on a transverse wave are called troughs.

• Expansion: When some particles travel through a medium in a longitudinal wave, an expansion is the maximum spacing between them.

• Compression: When some particles travel through a medium in a longitudinal wave, an expansion is the minimum spacing between them.

5. Can we measure the size of a Wavelength?

Wavelength is an essential measure of wave size. We can measure it as the distance between two neighboring compressions of the longitudinal wave or two adjacent crests of a transverse wave. We usually measure wavelength in meters, which is related to the wave's energy.

To find the wavelength of a particular wave, we divide the said wave's speed by its frequency.

We can also measure wavelength by the length from crest to crest, trough to trough, or just from a particular position from one wave to another.