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Are Light Waves Transverse or Longitudinal? The Interesting Answer!

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light waves taken on low shutter

When we talk about transverse or longitudinal waves, we’re really talking about the way in which energy travels through the waves. Light waves, or electromagnetic waves, are transverse waves. They are vibrations that occur in both the electric and magnetic fields. Electromagnetic waves travel at the speed of light through a vacuum—meaning they do not need a medium in which to travel in.

If you’d like to learn more about what this means and learn how longitudinal and transverse waves differ, keep reading!

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What Are Waves in Physics?

Waves are a way in which energy can transfer between stores. In physics, there are many types of waves, but we’ll be looking at the most commonly studied and known: mechanical waves, and electromagnetic waves.

Both mechanical and electromagnetic waves transfer energy, but they do not transfer matter. The best way to visualize this is by imagining two people, each holding one end of a slinky. If one person moves their hand up and down, the energy will travel through the slinky to the other person, but the slinky itself will remain intact—there’s no transfer of matter.

Mechanical Waves

In physics, mechanical waves are oscillations, or vibrations, through matter. Mechanical waves refer to the transfer of energy through a medium. Think of a ripple moving across the surface of the water. The movement of energy in a mechanical wave is limited by its medium, though it can pass through several. 

Let’s look at our slinky example again. The wave that is produced is a mechanical wave, because it travels through a medium. Sound is another example, because sound waves travel through air particles. Like all mechanical waves, sound cannot travel through a vacuum, which is why we can’t hear anything in space!

Electromagnetic Waves

Electromagnetic waves are oscillations, or vibrations, that occur along the electric and magnetic fields. These waves—light waves—can travel outside of a medium, through the vacuum of space, at the speed of light.

Electromagnetic waves are classified by the length of the waves (wavelength) and their frequency, into a spectrum that includes—from longest wavelength to shortest—radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays.

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What’s The Difference Between Transverse and Longitudinal Waves?

There are two ways in which energy can transfer through waves. Energy can transfer through mechanical waves that are either transverse or longitudinal. Electromagnetic waves are transverse.

longitudinal vs transverse wave illustration

Image Credit: VectorMine, Shutterstock

Transverse Waves

Looking back at the slinky example, imagine if the hand on either side was moving in an up-and-down motion. The wave of energy produced would travel through the slinky in a horizontal S shape, snaking as it moves forward. The waves themselves are moving up and down at a right-angle, or a 90-degree angle, to the direction that the energy is traveling in (in this case, forward).

Examples of transverse waves include light waves, waves in water, vibrations of strings on a string instrument, seismic S-waves, and even Mexican waves.

Longitudinal Waves

We’re going to use the slinky example one last time. For longitudinal waves, imagine a single push on one side of the slinky. The pressure would impact the next particle, and the next, on and on as the energy travels from one side to the other. Parts of the slinky would appear compressed (compression), while other parts are apart (rarefactions).

Instead of the particles vibrating or oscillating at a 90-degree angle, in longitudinal waves, the particles vibrate parallel to the direction in which the energy is traveling.

Sound is a perfect example of a longitudinal wave. Imagine a drum being struck. The vibration causes the particles in the air to vibrate, which then pushes against the next particle, and that one pushes the next until the energy reaches your ears, where it causes your eardrum to vibrate at the same frequency.

Seismic P-waves are another example of energy moving through longitudinal waves.

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In Summary

Light waves are an example of transverse waves, because the waves move at a 90-degree angle to the direction in which the energy is traveling. Light waves do not need a medium to transfer energy through—they can travel through vacuums, which is how we get light from the sun and the far-away stars in our universe.


Featured Image Credit: WrongTog, Unsplash

About the Author Cheryl Regan

Cheryl is a freelance content and copywriter from the United Kingdom. Her interests include hiking and amateur astronomy but focuses her writing on gardening and photography. If she isn't writing she can be found curled up with a coffee and her pet cat.

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