How Energy & Information is Transferred by Waves

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

This lesson explores how waves transfer energy but not mass. You will learn about how energy is transferred by waves, as well as understand the components of waves and see examples of different types of waves.

Waves Transfer Energy

Have you ever been at a sporting event when 'the wave' occurred? It's fun to watch everyone stand up when it's their turn, creating a wave that moves through the crowd. But have you ever stopped to think about this wave and how it works?

You may have noticed that while the wave itself works its way around the stadium, the people making the wave don't have to do anything but stand up and sit back down again. In other words, the people move vertically in their seats while the wave moves horizontally around the stadium.

Waves at sporting events move around the stadium without moving the people creating it
Mexican wave

This is because waves transfer energy and not mass. For example, a wave in the ocean doesn't transfer water particles from one place to another, but rather those particles are just moving up and down perpendicular to, or at a right angle to, the movement of the horizontal wave. This happens as energy is transformed from potential or 'stored' energy to kinetic or 'movement' energy, and then back to potential energy again.

Think about your participation in the stadium wave. You start at a seated position, which is potential energy. You then change to a standing position, converting that stored energy into movement or kinetic energy.

As you reach your full standing position, you slow down and once again your energy is being converted back to potential energy. As you sit back down, the energy is converted back to kinetic energy, and when you sit all the way down that energy becomes potential energy again.

A wave moves horizontally while the particles move vertically
a water wave

How Energy Is Transferred

So how does energy get transferred through a wave? Be it air, water, or otherwise, energy is transferred through the vibrations of the medium's particles. So a water wave transfers energy through the vibration of the water particles, sound waves travel through the vibration of air particles or the particles of a liquid or solid, and electromagnetic and magnetic fields vibrate to transfer energy through electromagnetic waves.

As you may know, not all waves are the same size, shape, or speed.

  • The amplitude of a wave is how tall a wave is from its rest position (NOT how tall the wave is from top to bottom).
  • The wavelength is the length of the wave measured from one point on the wave to the same point on the next wave. This could be from the crest (the top of one wave) to the crest of the next wave, or it could be from the trough (bottom of one wave) to the next. As long as it's the same point on each wave it doesn't matter where you measure it from.
  • Wave frequency is how often a wave is produced in each second, or the number of waves in that time frame.

The components of a wave
wave components

Examples of Energy Transfer

All of these terms are related to the amount of energy in a wave. For example, a water wave that has both a large amplitude (is very tall) and a long wavelength is a wave with a lot of energy. This is the case with tsunamis, which are dangerous water waves that pack a big punch.

Even though electromagnetic waves travel at the same speed, they can vary in their frequency and wavelength, a relationship that is inversely proportional, meaning as one gets larger the other gets smaller.

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