Waves

Preview Why Do We Care? Energy Without Matter The Simplest Wave Water vs. Wi-Fi Wave Movement Longitudinal Transverse Make it Mathematical

Why Do We Care? Waves are everywhere. Light, Sound, Music, Wi-Fi, Water, Grandfather Clocks, Slinkys, Earthquakes, Microwave Ovens, Cell Phones, Radio, Television, Gravity, Strings, Newton’s Cradle, Explosions, Lasers, Saying Hello to Your Friend, etc… Waves are a fundamental foundation of many aspects of math, physics, engineering, entertainment, and life.

Waves Transfer Energy

Energy Without Matter Waves like this move energy Fans become excited Nobody is running around the whole stadium Energy is being transferred without matter Individuals only moving a small amount, ‘vibrating’ Waves transfer energy without transferring matter. (Not like throwing a battery.) The individuals in the crowd can be thought of as particles/molecules in a wave. Animation shows crowd performing a ‘wave’ at a sporting event.

Types of Waves

The Simplest Wave Pendulum Single ‘particle’ oscillating Simple Harmonic Motion Sine curve Only length and g matter T = Period L = Length g = Accel. Due to Gravity Animation shows that shorter pendulums swing faster, even though they are the same mass.

Some waves use particles with mass, some don’t. Water vs. Wi-Fi Some waves use particles with mass, some don’t. Water Has mass Has matter Is Mechanical Wi-Fi No mass No matter Part of Electromagnetic spectrum (light) Can pass right through things, or a vacuum

Some waves use particles with mass, some don’t. Water vs. Wi-Fi Some waves use particles with mass, some don’t. Water Has mass Has matter Is Mechanical Wi-Fi No mass No matter Part of Electromagnetic spectrum (light) Can pass right through things, or a vacuum Other wave media? What is sound? Make sure to point out that air is a possible medium and SOUND IS MECHANICAL. Light can travel through space, but not sound because there is no medium.

Water vs. Wi-Fi Other wave media? What is sound? Some waves use particles with mass, some don’t. Water Has mass Has matter Is Mechanical Wi-Fi No mass No matter Part of Electromagnetic spectrum (light) Can pass right through things, or a vacuum Other wave media? What is sound? Metal, ground, strings, gas, air. Mechanical, can’t travel through vacuum. Make sure to point out that air is a possible medium and SOUND IS MECHANICAL. Light can travel through space, but not sound because there is no medium.

More than one way for particles to move. Wave Movement More than one way for particles to move. Top animation shows particles moving from left to right in longitudinal compression waves. Bottom animation shows particles moving up and down in a transverse wave.

Longitudinal Particles travel same direction as whole wave. Where do you see this daily? Animation shows particles moving up and down in a transverse wave.

Sound waves are Longitudinal. Point out that this shockwave is a combo of an air pressure wave and a sound wave.

Transverse Overall wave movement is perpendicular to particle movement. Electromagnetic waves are transverse How when non-mechanical? Animation shows particles moving up and down in a transverse wave.

EM waves effect surrounding particles in a perpendicular manner. Transverse Overall wave movement is perpendicular to particle movement. Electromagnetic waves are transverse How when non-mechanical? EM waves effect surrounding particles in a perpendicular manner. EM waves do not need a medium, but they affect what they travel through in a perpendicular way. While photon moves forward things around it move sideways.

Water/Liquids Circles Less movement deeper Combo of both Long. & Perp. Animation shows particles moving in a circular pattern.

What medium might have these elliptical waves? Rayleigh What medium might have these elliptical waves? Animation shows particles moving in an elliptical pattern.

Rayleigh What medium might have these elliptical waves? Jell-O, other misc. goop.

Wave Characteristics

Make it Mathematical Troughs, Crests, Nodes λ = nm, cm, etc… τ = sec, min, etc… = Hz, kHz, MHz (periods/sec, sec-1) Point out that wavelength and period can be measured from points other than crests.

Make it Mathematical Amplitude Transverse Longitudinal nm, cm, etc… Measures height from middle to crest Longitudinal dB, Measures pressure

Wave Speed=Wavelength * Frequency Make it Mathematical Wave Speed=Wavelength * Frequency Speed of Light = 299,792,458 m/s = 186,292 mi/s Constant, c Speed of Sound = 340 m/s = 0.21 mi/s Variable, depends on medium

Review Waves transfers energy without transferring matter. Waves can be mechanical and non-mechanical. Waves move in several different patterns. We use many variables to measure waves. Bill Nye!