Longitudinal & Transverse Waves Review

Define Waves

Types of Waves

Longitudinal Waves

Transverse Waves

Waves transfer energy from one place to another.

Waves start with a disturbance-

Waves are vibrations that transfer energy from one place to another, starting with a disturbance or vibration. Many waves transfer energy through a medium, such as solids, liquids, or gases, by causing the particles in the medium to vibrate.

Here’s something amazing about waves—they don’t move the particles in the medium (like air, water, or a solid) over long distances. Instead, they make the particles vibrate in place, passing energy to their neighbors like a relay race.

Energy travels long distances.

Particles move back and forth.

Select the arrow that represents the direction the energy travels in this slinky wave.

There are two main types of waves, and they transfer energy in different ways: Transverse waves: The particles move up and down or perpendicular to the wave’s direction. Longitudinal waves: The particles move back and forth or parallel to the wave’s direction.

Sound waves are a great example of a longitudinal wave. Here’s how they work: Sound waves are created when something vibrates, like vocal cords or a speaker. These vibrations push and pull on nearby air particles, creating areas of compression, where particles are pushed together, and areas of rarefaction, where particles are spread apart. These compressions and rarefactions travel outward as the sound wave, transferring energy.

Sound waves have three important properties that determine how they behave: frequency, wavelength, and amplitude. Frequency is the number of vibrations or compressions that occur per second and is measured in hertz (Hz). Higher frequency means a higher-pitched sound, while lower frequency produces a lower-pitched sound. Wavelength is the distance between two consecutive compressions or rarefactions; longer wavelengths result in lower-pitched sounds, and shorter wavelengths create higher-pitched sounds. Amplitude refers to the strength or intensity of the wave, which determines the loudness of the sound. Higher amplitude means louder sounds, while lower amplitude results in quieter sounds. Together, these properties define how we hear and experience sound.

Let’s look at another example of a longitudinal wave: a slinky. When you push and pull on one end of a slinky, you create areas where the coils are compressed together, called compressions, and areas where the coils are spread apart, called rarefactions. These compressions and rarefactions travel along the length of the slinky, transferring energy from one end to the other without the coils themselves moving far. This is similar to how sound waves move through the air, transferring energy through vibrations.

The particles move back and forth or parallel to the wave’s direction.

particles move back and forth

Let’s dive into transverse waves, another important type of wave. In transverse waves, particles move up and down or perpendicular to the direction the wave travels. This is different from longitudinal waves, where particles move back and forth along the wave’s direction.

A great example of a transverse wave can be demonstrated with a slinky. If you shake one end of the slinky side to side, you’ll see waves moving along its length. The coils move up and down, but the wave itself travels horizontally, showing the perpendicular motion of transverse waves.

For a slinky demonstrating a transverse wave, frequency refers to how many times you shake the slinky up and down in one second. A higher frequency creates more waves in a shorter amount of time. Wavelength is the distance between two consecutive crests, which are the highest points of the wave, or two consecutive troughs, the lowest points. Finally, amplitude is how far you move the slinky up or down from its resting position. A larger movement creates a wave with a higher amplitude, which means the wave carries more energy. These three properties—frequency, wavelength, and amplitude—work together to describe the motion and energy of the transverse wave on the slinky.

Light is a transverse wave that can travel through empty space without needing a medium like air or water. It forms when electric and magnetic fields vibrate at right angles to each other and to the direction the wave is traveling.

We call the different frequencies and wavelengths of light the electromagnetic (EM) spectrum, which includes all types of electromagnetic waves. At one end are radio waves, with the longest wavelengths, lowest frequencies, and lowest energy, used for communication like radio, TV signals, and cell phones. At the other end are X-rays and gamma rays, with very short wavelengths, high frequencies, and very high energy, used in medicine for imaging bones and internal organs, as well as in cancer treatments like radiation therapy. In the middle is visible light, the small range our eyes can see, from red (lower energy) to violet (higher energy). All these waves are part of the same spectrum, differing in wavelengths, frequencies, and energy.

In summary, waves transfer energy without moving matter over long distances. Transverse waves move particles perpendicular to the wave’s direction, while longitudinal waves move particles parallel. Waves are described by their wavelength, frequency, and amplitude, and can travel through solids, liquids, gases, or even empty space in the case of light waves.

Longitudinal Waves

A longitudinal wave is a type of wave in which the particles oscillate (vibrate back and forth) in the same direction that the wave propagates (moves).

Spring particles oscillate back and forth.

The wave carries energy through the spring.

A longitudinal wave in a toy spring happens when you push and pull one end of the spring. The coils oscillate (move back and forth) in the same direction that the wave travels, creating areas of compression (where the coils are close together) and rarefaction (where the coils are spread apart). This back-and-forth motion transfers energy along the spring.

A sound wave is a longitudinal wave because the particles in the air oscillate back and forth in the same direction that the wave travels, creating compressions and rarefactions as the energy moves outward.

Waves

A wave is a disturbance or variation that transfers energy from one point to another without transferring matter. For waves that travel through matter, it causes the particles in the material it travels through to oscillate, or move back and forth or up and down, while staying in place. The energy moves through the wave, but the particles themselves don’t travel with it.

Energy travels. The particles oscillate in place.

Transverse Waves

Spring particles oscillate at right angles (perpendicular) to the direction the wave travels.

A transverse wave is a type of wave in which the particles oscillate (move up and down or side to side) perpendicular to the direction that the wave propagates (moves).

The wave carries energy through the spring.

Electromagnetic (EM) waves, such as visible light and radio waves, are special transverse waves because they have electric and magnetic fields that move at right angles to each other and the wave’s direction. Unlike other waves, they don’t need a medium and can travel through space.

A transverse wave in a toy spring happens when you shake one end of the spring side to side or up and down. The coils oscillate (move side to side or up and down) perpendicular to the direction that the wave travels. This motion transfers energy along the spring while the coils stay in place and vibrate.

Electromagnetic Waves