Waves

What is a wave? A wave is a repeating disturbance or movement that transfers energy through matter or space (transfers energy-NOT matter) Types of waves 1. Water 5. Seismic 2. Sound 6. Radio 3. Light 4. Electromagnetic

What creates Waves? Anything that vibrates creates waves. A wave will only exist as long as it has energy to carry it. Vibrate: to move up & down/ back & forth in a rhythmic motion. Mechanical Waves: waves that travel only through matter-solids/liquids/gases or combination of them. Medium: the matter that waves travel through.

Two Types of Mechanical Waves Transverse wave: a wave where the matter in the medium moves back and forth at right angles to the direction the wave travels; water wave.

Compression wave: (longitudinal) a wave where matter in the medium moves back and forth along the same direction that the wave travels; sound waves. **The compression in a compression wave corresponds to the crest in a transverse wave***

Parts of a wave

How are waves different? Transverse wave: a. Crest: the highest point of a wave b. Trough: the lowest point of a wave c. Wave length: crest to crest or trough to trough d. Frequency: count the # crests or # troughs that pass a given point. Compression wave: a. Rarefaction: less dense region b. Compression: region where the coils are close together c. Wave length: rarefaction to rarefaction or compression to compression d. Frequency: count the # compressions or rarefactions that pass a

Frequency: units expressed in Hertz (Hz) Period: units expressed in seconds (s) * A frequency of 1Hz means one wave length passes by in one second* ** Increase wave frequency, the period decreases & the wavelength decreases**

Amplitude Amplitude: the amount of energy a wave carries. The > amplitude, the more energy a wave carries. How do you measure amplitude? a. Compression wave: how tightly the medium is pushed together. The denser the medium at compressions, the further apart they are at rarefactions, the > amplitude & the more energy the wave carries. b. Transverse wave: the distance from the crest/trough of the wave to it's rest position. The taller a wave, the > amplitude & the more energy the wave carries.

How do waves behave? A. Reflection: waves strike an object and bounce off it; echo sound waves. The Law of Reflection: the angle of incidence is = to the angle of reflection.

B. Refraction: waves bend when they have a change in speed when they move from one medium to another. (the > the change in speed, the more the wave bends).

C. Diffraction: when an object causes a wave to change direction and bends around it.

D. Interference: when 2 or more waves overlap and combine to form a new wave. a. Constructive Interference: 2 waves overlap and ADD together. b. Destructive Interference: 2 waves overlap and subtract from each other.

Standing Waves Standing Wave: wave patterns that occur when waves equal in wavelength & amplitude but moving in opposite directions continuously interfere with each other.

Resonance Resonance: when an object vibrates by absorbing energy at its natural frequencies.