Classification of Waves
Waves
Waves are disturbances that transfer energy from one place to another without transferring matter.
They can be classified based on how the particles of the medium move relative to the direction of wave propagation.
Transverse Waves: Particle Motion Perpendicular to Wave Propagation
In transverse waves, the particles of the medium oscillate perpendicularly to the direction of wave propagation.
Example- Water Waves:
- In water waves, the water molecules move up and down while the wave travels horizontally across the surface.
- Electromagnetic Waves:
- Light waves, radio waves, and X-rays are all transverse waves.
- In these waves, oscillating electric and magnetic fields are perpendicular to the direction of wave travel.
- Transverse waves can travel through solids and on the surface of liquids, but not through gases or within liquids.
- This is because gases and liquids do not have the structural rigidity needed to support perpendicular oscillations.
Longitudinal Waves: Particle Motion Parallel to Wave Propagation
In longitudinal waves, the particles of the medium oscillate parallel to the direction of wave propagation.
Example- Sound Waves:
- In sound waves, air molecules compress and rarefy as the wave travels through the air.
- Compression Waves in a Slinky:
- When you push and pull a slinky, coils move back and forth in the same direction as the wave.
Longitudinal waves can travel through solids, liquids, and gases because they rely on compressions and rarefactions, which all states of matter can support.
Compression
A compression is a region in a longitudinal wave where the particles of the medium are close together, resulting in a high-pressure area. In sound waves, compressions correspond to regions of increased air density and pressure.
Rarefaction
A rarefaction is a region in a longitudinal wave where the particles of the medium are spread apart, resulting in a low-pressure area. In sound waves, rarefactions correspond to regions of decreased air density and pressure.
Key Wave Parameters: Wavelength, Frequency, Time Period, and Wave Speed
To fully describe a wave, we need to understand several key parameters:
Wavelength ($\lambda$)
- The wavelength ($\lambda$) is the distance between two consecutive points in phase on a wave, such as crest to crest or trough to trough.
- It is measured in meters (m).
If the distance between two crests of a water wave is 2 meters, the wavelength of the wave is 2 m.
Crest
A crest is the highest point of a wave, where the displacement of the medium is at its maximum positive value relative to the equilibrium position. In a transverse wave, crests correspond to peaks in the wave motion.
Trough
A trough is the lowest point of a wave, where the displacement of the medium is at its maximum negative value relative to the equilibrium position. In a transverse wave, troughs correspond to the lowest points in the wave motion.
