Welcome Back Minions!!!

Recap: What are waves?A wave is a disturbance that

carries energy through matter and space.

The matter through which waves move through is called a MEDIUM. It can be a solid, liquid or gas.

Mechanical WavesWaves that require a medium are

called mechanical waves. Nearly all waves are mechanical

waves. Ex: ocean waves, sound waves and seismic waves

(earthquakes)Electromagnetic Waves are NOT

mechanical waves, so they do not need a medium to travel through!

Energy moving through a medium

• The picture above shows a medium made up of particles connected by springs. 

• As one individual particle is disturbed, it transfers the energy from that particle to the next and so on.

• So… energy is transported from one end of the medium to the other end of the medium without transporting any actual matter! 

• Ex: Like being in the ocean and a wave picks you up and puts you down as it passes by.

• Or Dominoes falling into each other

How mechanical waves move through matter…

The kind of medium, (solid, liquid, gas) determines the mechanical wave speed.

Waves rely on the elasticity and inertia properties of the medium. Basically how are the particles moving in

the medium?Which medium do mechanical waves

travel faster in, solids, liquids or gases? (*hint* think about molecules)

How mechanical waves move through matter…

Solid mediums! Because..in solids and liquids the molecules are more closely packed together than gases, so energy is transferred from one particle to another particle faster.

So which medium do mechanical waves travel through the slowest?

Gases! Because… the particles are moving rapidly and randomly it is hard for the particles to transfer the energy to one another!

Faster than the Speed of Sound! In the air, sound will generally

travel 300 meters per second. In the liquids, sound will generally

travel 1500 meters per second. In the solids, sound will generally

travel 2500 meters per second.

Bouncing back…Echo

A reflected sound wave. Harder/Smoother surface, better echo Softer/Uneven surface, not as good or

none.

EchoUses

Fish Finder Cardiogram Ultrasound Detect/Measure

Earthquakes Echolocation SONAR

Using waves to detect defects in man-made structures.

Break in the rail line

Ever notice…Ambulance coming towards you, then

driving by and going away from you…What did you notice?

Doppler EffectDoppler Effect

The change of a frequency of a wave as the source moves in relation to the observer.

If moving towards the observer… Frequency increases. (Higher Pitch)

If moving away from observer… Frequency decreases. (Lower Pitch)

Doppler EffectExplain to me how it works…

Breaking the Sound Barrier

Faster than the speed of sound…You have seen the pictures…

The sound that goes boom…Sonic Boom

Explosive sound when a shockwave reaches your ears.

Faster than speed of sound Overcome compressed soundwaves

Shocking!Shockwave

Overlapping soundwaves that result in a mechanical wave with high pressure and high energy.