Unit 7 –Lecture 3

ClaritySubstances have varying levels of clarity –

transparent materials allow waves to pass through with minimum or no distortion

ClaritySubstances have varying levels of clarity –

translucent materials allow waves to pass through them with varying degrees of distortion

ClaritySubstances have varying levels of clarity –

opaque materials do not allow waves to pass through themwaves must be

reflected or absorbed

Reflectionoccurs when a wave strikes an object and

bounces off of itechos (& echolocation)image in mirror

ReflectionLaw of Reflection

the angle of incidence [input] must equal the angle of reflection [output]

Mirrorsmirrors must be smooth so all the angles line

up to make a clear picture in the reflection [plan(e/ar)]

Smooth Surface Rough Surface

MirrorsConcave

“caved in”light rays, etc., converge in the centermake the image larger or focus energy

MirrorsParabolic

Satellite dishesLighting the Olympic Torch

MirrorsConvex

“curved out”Light rays, etc., spread out from the centerImages look smaller, but cover more area

Mirrors

Refractionbending of a wave as it moves from one

medium to anotherthe image difference is caused by a change

in the speed of the wave

Refraction“edges” of wave “slow down” in a more dense

medium and “speed up” in a less dense mediumbends towards

the “normal” in a more dense medium

away from the “normal” in a less dense medium

Refractiondepends on the

type of mediumthe angle the wave hits the medium

waves of light move faster through air than through water

RefractionLaw of Refraction

RefractionOil & Gasoline Rainbows

because of the different densities of oil, gasoline, water, and air, a rainbow-like refraction can form in puddles near well-traveled parking lots

RefractionLenses act to control the refraction of light to

focus it in a more desirable manner.

Diffractionthe bending of waves around a barrier

if 1 edge, only one curveif 2 edges, both

will bend the wave

Diffraction

Interferencecaused by the passing of two waves through

one anotherhow the waves line up determines how they

will interact

Interferenceconstructive interference –

crests and troughs line up build on one anotherare said to be “in phase”

Interferencedestructive interference –

crests and troughs don’t line uplessen one anothersaid to be “out of phase”

if they are exactly opposite, they will cancel each other out

Interference

HomeworkFINISH YOUR WAVES PACKET

We will be going over it on Monday.

complete worksheet on back of notes

study for upcoming test = Weds next week