The Energy of Waves

• Wave

The Nature of Waves

• • periodic disturbance in a solid, liquid, or gas energy being transferred through a medium or empty space • Medium • substance through which a wave can travel

• Mechanical waves • Electromagnetic waves • • waves that require a medium ex. sound waves • • do not require a medium travel through emptiness of space and matter

Types of Waves

• Transverse waves • • particles move perpendicularly to the direction the wave is traveling (up & down) ex. electromagnetic waves • highest point on wave 1. Crest • lowest point on wave 2. Trough

• Longitudinal Waves • • particles vibrate parallel to the direction of wave motion (back & forth) ex. sound waves 1. Compression • particles are pushed together 2. Rarefaction • particles are spread apart

• Surface Waves • Combination of transverse and longitudinal waves • Wave motion is circular • Example-Ocean Wave

• Amplitude

Properties of Waves

• • • related to height max distance from rest position waves with large amplitude carry more energy

• • Wavelength Frequency • • distance between two crests or two compressions shorter wavelengths = more energy • • • • # of waves in a given time measured in hertz (Hz) 1 Hz = 1 wave/sec high frequency = more energy

• Wave Speed • speed at which wave travels • speed = wavelength x frequency •

v = λ x f

• wavelength and frequency are inversely related

• Reflection

Wave Interactions

• • wave bounces back after hitting a barrier all waves can reflect • Echo • reflected sound waves

• Refraction • bending of a wave as the wave passes from one medium to another at an angle • wave speed and wavelength changes • ex. rainbows – sunlight refracted through water droplets

• Diffraction • bending of waves around a barrier or through an opening • depends on wavelength and size of barrier • ex. sound waves can be heard because they have longer wavelengths than light waves

• • Interference • Constructive Interference Destructive Interference • two or more waves overlapping • waves overlap to make larger crests/troughs – larger amplitude • • crest of one wave overlaps the trough of another = smaller amplitude waves with same crest/trough = no wave at all

• Standing Waves • • • pattern of vibration that simulates a wave that is standing still only looks like it is still ex. musician plucks a guitar string • Resonance • • two objects naturally vibrate at the same frequencies ex. singing in the shower