Wave Wave InteractionsInteractions

Waves All Around Us

Imagine you just spent a day at the beach with your family. You had a blast playing in the ocean, laying out in the sun, listening to music and talking with your family. When you go back to the condo, you heat up some pizza in the microwave and turn on the TV.

Can you name all the different waves that were present in your day on the beach?

Standard

S8P4. Students will explore the wave S8P4. Students will explore the wave nature of sound and electromagnetic nature of sound and electromagnetic radiation. radiation. B. Describe how the behavior of light B. Describe how the behavior of light

waves is manipulated causing reflection, waves is manipulated causing reflection, diffraction, refraction, and absorption.diffraction, refraction, and absorption.

Review

From the list of waves you just named, can you identify whether it is electromagnetic or mechanical?

What is the difference between electromagnetic waves and mechanical waves?

Which one needs a medium? What is a medium? Name 3. Which one causes vibrations?

Reflection Waves bounce back All waves can be reflected We can see objects because of the visible

light waves that are bounced off of them Waves bounces back at the same angle

as it hits the object Angle of incidence

(original wave) Angle of reflection

(bounce back)

Scattering Scattering

A type of reflection Waves collide with matter and reflect in many

different directions Blue sky – shortest wave length of visible light

scattered by particles

in the atmosphere

Refraction

Wave bends as it is transmitted Due to different wave speeds in different

mediums gas to solid, gas to liquid

Causes optical illusions

Refraction Rainbow

When white light waves separate by refraction,

we see colors

Diffraction Most times waves travel in

a straight line Can bend around a barrier

Edges of the object are blurry Example – eclipse, x-ray

Can bend through an opening Sound waves are much longer

than light waves Sound waves bend more

Absorption

Absorption Transfer of energy to an object

light to heat light to chemical (by plants with photosynthesis) light to battery to electrical (by solar panels)

Soaks up waves Makes waves dimmer –

loss of energy

Interference

Overlapping waves Share space Either increases amplitude – constructive

The “thump” from the car stereo next to yours. Or, decreases amplitude – destructive

You may not hear the person sitting two seats away from you when the cafeteria is crowded.

Constructive interferenceConstructive interference happens when waves add up to make a happens when waves add up to make a

larger amplitude.larger amplitude. Suppose you make two wave pulses on a Suppose you make two wave pulses on a

stretched string. stretched string. One comes from the left and the other One comes from the left and the other

comes from the right. comes from the right. When the waves meet, they combine to When the waves meet, they combine to

make a make a single large pulsesingle large pulse..

Destructive interferenceDestructive interference What happens when one pulse is on top of What happens when one pulse is on top of

the string and the other is on the bottom? the string and the other is on the bottom? When the pulses meet in the middle, they When the pulses meet in the middle, they

cancel each other out.cancel each other out. During During destructive interferencedestructive interference, waves add , waves add

up to make a wave with smaller or zero up to make a wave with smaller or zero amplitude.amplitude.