Energy Travels in Waves

It doesn’t matter what form energy might take on, when it is time for energy to travel somewhere, it will do so in the form of a wave!

There are two parts of a wave that are very important for us to understand. They will help us learn more about the type of energy involved and how much energy is involved. The two parts are:

1. Wavelength, and 2. Amplitude

Two Types of Waves

Transverse

Longitudinal (Compression)

Transverse Waves

A Transverse Wave moves up and down from the line of progression. The wave travels away from it’s source, rising above and falling below what would be the resting state, if there were no energy at the time.

Think of what happens when you are riding in a car and you hold your hand outside the window. Your hand moves up and down as you travel, much like a wave.

Wavelengths

Wavelengths can help us know more about the energy that is traveling. For example, an AM Radio wave has a long wavelength and can travel long distances when there is minimal interference. Similarly, an FRS (a good walkie-talkie) radio is only able to transmit for short distances because it uses a short wavelength and lower power. X-rays have very short wavelengths, and visible light waves are short also, however, the wavelengths vary between the different colors of light.

Wavelength is the distance from a point on one wave, to the corresponding pointon the next wave.

Amplitude

The second trait we will study is amplitude (the measure of the amount of energy in a wave). In a transverse wave, amplitude is the measure from the resting position to either the crest (high point of the wave) or to the trough (low point of the wave.)

The concept of measuring how far molecules move is much more difficult, so amplitude is usually only discussed in terms of transverse waves.

Example of the Ocean

We can also think of amplitude in terms of a boat bobbing in the waves of the ocean.

The bigger (taller) the wave, the higher the amplitude, and the more the boat will move up and down! It takes energy to move a boat and the water. But you'll notice the boat stays in the same place, it only goes up and down. This is because the energy that made the wave is transferring through the water, it is not transferring the water. The water is the medium that the energy is being transferred though. The definition of a wave is: "transfer of energy through matter or space."

Smaller waves cause less movement because they have less energy, or a smaller amplitude. Larger waves, like a tsunami, hold a huge amount of energy. That is why they are so damaging.

High vs. Low Frequencies

Let's use an analogy to think about the waves on the ocean. Picture what happens to a small boat bobbing on the ocean. If the distance between the wave crests is large (i.e. the wavelength is long), then the boat bobs up and down less often (the frequency is

low). If the distance is small (i.e.

the wavelength is short), then the boat bobs up and down more often (the frequency is high).

Longitudinal (Compression) Waves

The other wave is known as a Longitudinal (or Compression) Wave. It moves back and forth in the line of direction, not up and down like the transverse wave. If you take a slinky, lay it on the table, pull back about 10 links and let loose, you’ll observe a longitudinal wave. Notice that the slinky has areas that are darker where the rings have compressed (compression), and areas where it is stretched out (rarefaction). Longitudinal waves are sometimes referred to as compression waves for this reason.

How Energy Travels

Energy travels in several forms including:

LIGHT

SOUND

HEAT

EARTHQUAKES

LIGHT

Light waves are transverse and they can travel through solids, liquids, gases and a vacuum (space). LIGHT

SOUND

Sound waves are longitudinal; they can only travel in solids, liquids and gases.

SOUND

HEAT

Heat waves are very similar to light as they are transverse and travel through every medium (a medium is what the wave travels through- rocks, water, air etc.)

HEAT

EARTHQUAKES

Earthquake waves come in three different varieties, primary waves, secondary waves and surface waves. P-waves are longitudinal, S-waves and L-waves (surface) are both transverse.

EARTHQUAKES