Section 1 & 2: The Nature of Waves

Waves A wave is a repeating disturbance or movement that transfers energy through matter or space. A wave will only travel as long as it has energy to carry. Some waves need a medium to transfer through. A medium is matter like solids, liquids or gasses (or a combination of the above) that the wave travels through. Not all waves require a medium, but mechanical waves do require a medium.

The Two Types of Mechanical Waves 1. Transverse waves – These are waves that travel back and forth at right angles to the direction that the wave travels. Light is type of transverse wave.

Second Type of Wave 2. Longitudinal Waves – In these waves, the medium moves back and forth in the same direction that the wave travels. Sound waves are longitudinal waves.

Sound Waves Sound is transmitted as molecules are pushed together by vibrations. The more dense the material, the faster sound can travel.

Water Waves Water waves are generally classified as transverse waves, but they are not purely transverse. When water moves in waves, things that are floating on the surface generally travel in a circular motion.

Parts of a Transverse Wave A transverse wave can be divided into many different parts. A crest (peak) is the highest point in a wave. A trough is the lowest point in a wave. Amplitude is the size of the wave and indicates the amount of energy carried by the wave. A wavelength is the distance from a point on a wave to the nearest point just like it.

Frequency of a Longitudinal Wave Longitudinal waves do not have crests and troughs. Instead, when dense regions form in longitudinal waves, we refer to these as the compressions. The areas where the waves are less dense are known as rarefactions. Rarefaction Compression

Amplitude and Energy Amplitude is the measure of the energy transferred by the wave. In longitudinal waves, amplitude is related to how tightly pushed together the medium is at the compressions. In transverse waves, the height of the crests and troughs demonstrates the amount of energy (amplitude) the wave carries.

Frequency of a Wave Frequency is the number of wavelengths that pass a fixed point each second. Frequency is measured in hertz (Hz). If a wavelength passes a given point 10 times in a second, then that wavelength is said to be traveling at 10 Hz. Hz = # of wavelenghts/second

The Relationship between Wavelength and Frequency Wavelength and frequency have an inverse relationship. As frequency increases, wavelength decreases. As wavelength increases, frequency decreases.