What travels in traveling wave?

Answer 1

Lots and Lots of things but basically energy travels in a wave.

There are two types of wave those that require something to travel through and those that don't. Both types basically move energy from one point to another. Waves in water (or rock since I notice this has been tagged for earthquakes) move through the substance without carrying it along with them.

Think skipping ropes, if you hold one end and flick you get a wave travelling along the rope. The rope moves up and down as the energy passes through but restores to it's position afterwards. Water (slightly different), Rock (shockwaves) and Air (sound travels as a wave in air - in space no-one can hear you scream!) all do this.

Waves can also travel in a vacuum. In this case it is a change in electric or magnetic properties that makes it wave like. The maths is however the same so we treat them as waves.

Answer 2

Waves carry energy

In the most basic sense, both kinetic and potential energy are usually transported in waves.

Materials Waves:

In any material thing that is vibrating, there is motion of mater and hence kinetic energy. But, just as there is kinetic energy in a swing or pendulum, there is an periodic exchange of energy between potential and kinetic. All waves associated with material vibrations have both.

The potential energy in material waves is almost always elastic energy.

Almost all examples of waves in matter are compression or elastic waves.

Compression in waves means that the oscillations of matter in the medium are variations in density, or alternatively we can say these are periodic surfaces of compression and rarefaction.

Such is the case for sound in air or any gas or other fluid.

When the medium is a fluid, then the fluid is compressed and rarefied in a manner that varies periodically in space and time.

The other example is the case for sound in a solid. When the medium is a solid, then the solid is compressed and rarefied in a manner that varies periodically in space and time.

It is typical to call the potential energy stored by compressing a fluid as compression energy and it is typical to call the potential energy stored by compressing a solid elastic energy. Really, they are the same.

Elastic energy is just the sort of potential energy you get when compressing a spring. The medium opposes compression storing potential energy and exerts a force to return the medium thereby moving the medium in the direction of force and hence doing work. The work creates kinetic energy of matter in a material wave.

In the above, discussing energy as a result of compression assumes that the compression is relatively mild and does not change the basic structure of the material, i.e. it doesn't break if it is a solid and it does not change chemically due to compression.

There are other elastic properties than compression and these include shear and bend. There are waves associated with shear and bend and those waves also store elastic potential energy and waves formed exchange kinetic energy with the stored potential energy.

Surface Waves:

Water waves are an example of a surface wave where the interchange of potential and kinetic energy involves gravitational potential energy. Clearly, when the surface of the water has peaks and troughs, the peaks have matter that is at a higher potential energy than water at the level of the trough. As the wave moves, the peaks fall which causes water to move downward and have kinetic energy, but at the same time, water is moving upward to form the peak further along the direction of motion and that requires water movement and conversion of kinetic energy to potential energy.

Ripples:

Interestingly, very tiny waves, i.e. ripples, have another energy component. Ripples are strongly affected by surface tension. Surface tension provides a restoring force, lifting up troughs and pulling down peaks, much like membrane of a drum wants to remain flat. Water tension is not an elastic energy however. It derives from the forces of attraction between that atoms in the liquid, e.g. water molecules. Making more surface area costs energy by separating fluid molecules from their neighbors. The fluid gains potential energy with more surface area and the restoring force of surface tension is created by the fluid molecules trying to move more molecules closer to each other to lower potential energy. There is still gravitational potential energy as well in this example of ripples and the exchange of potential and kinetic energy.

Electromagnetic Waves:

Electromagnetic waves are the vibration of electromagnetic fields, a process that can occur in a vacuum or in matter. Assuming the electromagnetic wave is not absorbed as it passes through matter, the nature of the energy is basically the same as in vacuum.

It is a pretty complicated thing to prove mathematically, but an electromagnetic wave carries energy and momentum. The energy is, of course, electromagnetic energy.

It is sometimes convenient to discuss electromagnetic waves as photons, recognizing the quantum mechanical aspects of light. In that case, the energy is still electromagnetic, but it is discretized into individual packets or photons with the energy of each being Plank's constant, h, times the frequency of the light.
light an sound

Answer 3

Waves carry energy

In the most basic sense, both kinetic and potential energy are usually transported in waves.

Materials Waves:

In any material thing that is vibrating, there is motion of mater and hence kinetic energy. But, just as there is kinetic energy in a swing or pendulum, there is an periodic exchange of energy between potential and kinetic. All waves associated with material vibrations have both.

The potential energy in material waves is almost always elastic energy.

Almost all examples of waves in matter are compression or elastic waves.

Compression in waves means that the oscillations of matter in the medium are variations in density, or alternatively we can say these are periodic surfaces of compression and rarefaction.

Such is the case for sound in air or any gas or other fluid.

When the medium is a fluid, then the fluid is compressed and rarefied in a manner that varies periodically in space and time.

The other example is the case for sound in a solid. When the medium is a solid, then the solid is compressed and rarefied in a manner that varies periodically in space and time.

It is typical to call the potential energy stored by compressing a fluid as compression energy and it is typical to call the potential energy stored by compressing a solid elastic energy. Really, they are the same.

Elastic energy is just the sort of potential energy you get when compressing a spring. The medium opposes compression storing potential energy and exerts a force to return the medium thereby moving the medium in the direction of force and hence doing work. The work creates kinetic energy of matter in a material wave.

In the above, discussing energy as a result of compression assumes that the compression is relatively mild and does not change the basic structure of the material, i.e. it doesn't break if it is a solid and it does not change chemically due to compression.

There are other elastic properties than compression and these include shear and bend. There are waves associated with shear and bend and those waves also store elastic potential energy and waves formed exchange kinetic energy with the stored potential energy.

Surface Waves:

Water waves are an example of a surface wave where the interchange of potential and kinetic energy involves gravitational potential energy. Clearly, when the surface of the water has peaks and troughs, the peaks have matter that is at a higher potential energy than water at the level of the trough. As the wave moves, the peaks fall which causes water to move downward and have kinetic energy, but at the same time, water is moving upward to form the peak further along the direction of motion and that requires water movement and conversion of kinetic energy to potential energy.

Ripples:

Interestingly, very tiny waves, i.e. ripples, have another energy component. Ripples are strongly affected by surface tension. Surface tension provides a restoring force, lifting up troughs and pulling down peaks, much like membrane of a drum wants to remain flat. Water tension is not an elastic energy however. It derives from the forces of attraction between that atoms in the liquid, e.g. water molecules. Making more surface area costs energy by separating fluid molecules from their neighbors. The fluid gains potential energy with more surface area and the restoring force of surface tension is created by the fluid molecules trying to move more molecules closer to each other to lower potential energy. There is still gravitational potential energy as well in this example of ripples and the exchange of potential and kinetic energy.

Electromagnetic Waves:

Electromagnetic waves are the vibration of electromagnetic fields, a process that can occur in a vacuum or in matter. Assuming the electromagnetic wave is not absorbed as it passes through matter, the nature of the energy is basically the same as in vacuum.

It is a pretty complicated thing to prove mathematically, but an electromagnetic wave carries energy and momentum. The energy is, of course, electromagnetic energy.

It is sometimes convenient to discuss electromagnetic waves as photons, recognizing the quantum mechanical aspects of light. In that case, the energy is still electromagnetic, but it is discretized into individual packets or photons with the energy of each being Plank's constant, h, times the frequency of the light.
light an sound