Longitudinal and transverse waves Notes

How Do Waves Transfer Energy Without Moving Matter?

1. Waves are one of the most useful models in physics because they describe how energy and information can travel from place to place without transporting matter overall.
2. When light reaches your eyes or sound reaches your ears, what arrives is wave energy, not a stream of material that makes you heavier.

What is a Wave?

1. A wave is a process that transfers energy from one location to another.
2. When a wave travels, the energy moves through the medium, but the material itself does not travel with the wave.
3. The particles of the medium only vibrate about fixed positions as the wave passes.
4. After the wave has passed, particles return to their original positions.
5. This explains why waves can travel long distances without moving the material across those distances.

The Role of the Medium in Wave Motion

1. A medium can be a solid, liquid, or gas, depending on the type of wave.
2. Particles in the medium are already present before the wave starts.
3. As the wave passes, particles temporarily vibrate and then return to their original positions.
4. The medium itself does not travel with the wave.

How Particle Motion Transfers Energy

1. When energy is introduced into a medium, the nearest particles begin to vibrate.
2. These vibrating particles collide with or influence neighbouring particles.
3. Energy is passed from one particle to the next through these vibrations.
4. This process continues, allowing the wave to move forward through the medium.
5. Each particle only vibrates for a short time and then returns to rest.

Classifying Waves by Particle Motion

1. Waves are classified based on how particles move compared to the direction the wave travels.
2. The direction of wave travel is the direction energy moves.
3. The direction of particle vibration may be the same as or different from wave travel.
4. Based on this relationship, waves are divided into two main types:
   1. Transverse waves
   2. Longitudinal waves

Transverse Waves: Medium Motion Is Perpendicular To Wave Travel

1. In transverse waves, particle motion and wave motion are at right angles to each other.
2. The wave travels forward through the medium.
3. Particles vibrate perpendicular to the direction of energy transfer.
4. This perpendicular motion produces an up-and-down or side-to-side wave shape.
5. Transverse waves are often easy to observe and model.

Understanding the Shape of a Transverse Wave

1. Specific terms are used to describe particle positions in transverse waves.
2. A crest is the point where particles are displaced the furthest in one direction.
3. A trough is the point where particles are displaced the furthest in the opposite direction.
4. These features move through the medium as energy is transferred.

Longitudinal Waves: Medium Motion Is Parallel To Wave Travel

1. In longitudinal waves, particle motion and wave motion are in the same direction.
2. The wave travels forward through the medium.
3. Particles vibrate parallel to the direction of energy transfer.
4. Particles repeatedly move closer together and further apart.
5. This motion creates regions of high and low particle density.

Understanding Compressions and Rarefactions

1. Longitudinal waves are described using regions of particle spacing.
   1. A compression occurs when particles are pushed close together.
   2. A rarefaction occurs when particles are spread further apart.
2. These regions move through the medium as the wave travels.

Comparing Transverse and Longitudinal Waves

1. In transverse waves, particles vibrate perpendicular to wave travel.
2. In longitudinal waves, particles vibrate parallel to wave travel.
3. Both types of waves:
   1. Transfer energy
   2. Require particle vibration
   3. Do not transport matter overall

Wave Direction vs Particle Motion

1. The wave travels in the direction in which energy is transferred.
2. Particles vibrate around fixed positions.
3. Particle motion does not show the path of the wave.