2. What are Waves? A wave is a disturbance that transfers energy from place to place. Energy – the ability to do work The material through which a wave travels is called a medium. Examples of mediums: Gases (air), liquids, solids Waves that require a medium are called mechanical waves. Mechanical waves are produced when a source of energy causes a medium to vibrate. Vibration – a back and forth or up and down motion

3. Types of waves Waves are classified by how they move. Transverse waves move the medium perpendicular (right angles) to the direction in which the waves travel.

4. Transverse Waves The highest part of a transverse wave is called a crest. The lowest part of a transverse wave is called a trough.

5. Longitudinal Wave Longitudinal waves move the medium parallel to the direction in which the waves travel. Compressions – areas of the wave in which the coils are close together Rarefactions – areas of the wave in which the coils are spread out

6. Properties of Waves Amplitude – the maximum distance the particles of the medium carrying a wave move away from their rest position. Wavelength – the distance between two corresponding parts of a wave. (crest-to-crest, trough- to-trough) (compression-to-compression, rarefaction- to-rarefaction) Frequency – the number of complete waves that pass a given point in a certain amount of time. Speed – how far the wave travels in one unit of time.

7. Frequency, Wavelength & Amplitude

8. Formulas Speed = wavelength x frequency (S = W x F) Frequency = Speed / Wavelength (F = S / W) Wavelength = Speed / Frequency (W = S /F)

9. Solve 1. A wave with a frequency of 60.o Hz travels through a slinky with a wavelength of 0.90 m. What is the speed of this wave? 2. A drum is struck, producing a wave with a wavelength of 1.1 m and a speed of 5.5 m/s. What is the frequency of the wave? 3. The lowest pitch that the average human can hear has a frequency of 20.0 Hz. If sound with this frequency travels through air with a speed of 331 m/s, what is its wavelength?