Bellwork (4/22)Bellwork (4/22)

What is interference?What is interference? The result of the The result of the

superposition of two or superposition of two or more wavesmore waves

Waves Demos and Waves Demos and NotesNotes

4/22/144/22/14

Mechanical WavesMechanical Waves

The energy of the wave The energy of the wave travels through the travels through the mediummedium

The medium itself stays in The medium itself stays in the same locationthe same location

Mechanical WavesMechanical Waves

SlinkySlinky Seismic (Earthquakes)Seismic (Earthquakes) Water ripples (Surface waves)Water ripples (Surface waves) Ocean WavesOcean Waves SoundSound String or rope String or rope

Mechanical vs. EM Mechanical vs. EM waveswaves Mech. Waves NEED a medium Mech. Waves NEED a medium

to travel throughto travel through EM Waves don’t need a EM Waves don’t need a

mediummedium Mech. Longitudinal waves can Mech. Longitudinal waves can

propagate in fluids and solidspropagate in fluids and solids Mech. Transverse waves can Mech. Transverse waves can

propagate only in solidspropagate only in solids

Bellwork (4/24)Bellwork (4/24)

What is the physics concept What is the physics concept behind 3-D movies?behind 3-D movies?

Light PolarizationLight Polarization

Today’s AgendaToday’s Agenda

Finish the ActivityFinish the Activity Go over notes from Go over notes from

Yesterday’s Activity Yesterday’s Activity Start the next labStart the next lab

Properties of Properties of LightLight4/24/144/24/14

Part III: Polarization Film1) Hold up one polarization film up to the

overhead light and rotate around in a circle and record your observations.

2) Hold up two polarization films up to the overhead light and rotate one around in a circle while keeping the other in the same orientation and record your observations.

3) Repeat steps 1 and 2 but use the Smart Board as the light source?

4) Repeat steps 1 and 2 but use the Computer monitor as the light source?

BellworkBellwork

What is the physics concept What is the physics concept behind 3-D movies?behind 3-D movies?

Light PolarizationLight Polarization

Today’s AgendaToday’s Agenda

Notes from Yesterday’s Notes from Yesterday’s ActivityActivity

Start the next labStart the next lab

Properties of Properties of LightLight4/24/144/24/14

Light and Color Pre-Light and Color Pre-QuizQuiz

1.1. Light is a mechanical wave.Light is a mechanical wave.

2.2. All objects emit EM waves.All objects emit EM waves.

3.3. Light is a particle.Light is a particle.

4.4. White light is the absence White light is the absence of colors.of colors.

5.5. Only light has photons.Only light has photons.

Light and Color Pre-Light and Color Pre-QuizQuiz

6.6. Light travels slower in glass Light travels slower in glass then air.then air.

7.7. All colors of visible light have All colors of visible light have the same wavelength.the same wavelength.

8.8. Radio waves and sound waves Radio waves and sound waves are the same type of wave.are the same type of wave.

9.9. Our minds are capable of Our minds are capable of filling in information that is filling in information that is not there.not there.

10.10. The oceans makes our sky The oceans makes our sky appear blue.appear blue.

Light and Color Pre-Light and Color Pre-QuizQuiz

1. Light is a mechanical wave.1. Light is a mechanical wave. FalseFalse2. All objects emit EM waves.2. All objects emit EM waves. TrueTrue3. Light is a particle.3. Light is a particle. Somewhat TrueSomewhat True4. White light is the absence of 4. White light is the absence of

colors.colors. FalseFalse

Light and Color Pre-Light and Color Pre-QuizQuiz

5. Only light has photons.5. Only light has photons.

FalseFalse

6. Light travels slower in glass then 6. Light travels slower in glass then air.air.

TrueTrue

7. All colors of visible light have the 7. All colors of visible light have the same wavelength.same wavelength.

FalseFalse

Light and Color Pre-Light and Color Pre-QuizQuiz

8. 8. Radio waves and sound waves Radio waves and sound waves are the same type of waveare the same type of wave..

FalseFalse9. Our minds are capable of filling 9. Our minds are capable of filling

in information that is not there.in information that is not there. TrueTrue10. The oceans makes our sky 10. The oceans makes our sky

appear blue.appear blue. FalseFalse

Typoglycemia

• Can you read the following?

I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg. Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be in the rhgit pclae. The rset can be a taotl mses and you can sitll raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh? Yaeh and I awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins can raed tihs too.

Blind SpotBlind Spot

Focus on the text or a single Focus on the text or a single letterletter

Move the closer and farther Move the closer and farther from you until the black dot from you until the black dot disappears disappears

What is Light?What is Light?

Light:Light: is range of EM radiation is range of EM radiation that can be detected by the that can be detected by the human eye.human eye.

The PhotonThe Photon

PhotonPhoton: A wave packet : A wave packet (quantum) of an EM radiation (quantum) of an EM radiation (ex. radio, light)(ex. radio, light)

Travel at the speed of lightTravel at the speed of light Have energyHave energy Considered to be Considered to be bothboth a a

particleparticle and a and a wave wave !!

Light TransmissionLight Transmission

Transmission – the process of Transmission – the process of EM waves passing through a EM waves passing through a materialmaterial

Light TransmissionLight Transmission

The energy of light transfers The energy of light transfers energy (vibrations) to electrons energy (vibrations) to electrons

Transparent materials have Transparent materials have electrons in the material that electrons in the material that match the frequencies of the match the frequencies of the light (E&M wave) light (E&M wave)

These photons reemit the light These photons reemit the light through the materialthrough the material

Light TransmissionLight Transmission

Light (EM waves) will be Light (EM waves) will be absorbed (into heat) if the absorbed (into heat) if the frequencies frequencies do notdo not match. match.

(page 410)(page 410)

Light TransmissionLight Transmission

Transparent:Transparent: The physical The physical property of allowing EM waves to property of allowing EM waves to reemit (pass) through a material reemit (pass) through a material

Translucent:Translucent: Allows diffused EM Allows diffused EM waves to pass through the waves to pass through the materialmaterial

Opaque:Opaque: Does not allow EM Does not allow EM waves to pass throughwaves to pass through

Light TransmissionLight Transmission

Plastic film (transparent)Plastic film (transparent) Grocery bag (translucent)Grocery bag (translucent) Printer paper (translucent)Printer paper (translucent) Construction paper (opaque)Construction paper (opaque) Black Plastic (opaque)Black Plastic (opaque) Aluminum foil (opaque)Aluminum foil (opaque)

Light ReflectionLight Reflection

Reflection - The turning back Reflection - The turning back of EM waves at a surface.of EM waves at a surface.

Light ReflectionLight Reflection

Metals have free electrons to Metals have free electrons to vibrate and reemit the lightvibrate and reemit the light

Other materials absorb most Other materials absorb most of the light without much of the light without much remissionremission

Types of ReflectionsTypes of Reflections

Specular reflectionsSpecular reflections – reflect – reflect the light in the same forward the light in the same forward parallel direction (mirrors)parallel direction (mirrors)

Diffuse reflectionsDiffuse reflections – reflect – reflect the light in many different the light in many different directionsdirections

(non glossy paper)(non glossy paper)

Light ReflectionLight Reflection

Black plastic (mostly specular)Black plastic (mostly specular) Aluminum foil (somewhat Aluminum foil (somewhat

specular)specular) Plastic film (somewhat Plastic film (somewhat

specular)specular) Grocery bag (diffused)Grocery bag (diffused) Printer paper (diffused)Printer paper (diffused) Construction paper (diffused)Construction paper (diffused)

““How do we see How do we see objects?”objects?”

Light has to be emitted from a Light has to be emitted from a sourcesource

Light is absorbed / transmitted Light is absorbed / transmitted by the objectby the object

Light then is reemitted from Light then is reemitted from the objectthe object

This is what we see!This is what we see!

Light PolarizationLight Polarization

Light PolarizationLight Polarization: The : The alignment of EM waves where alignment of EM waves where their electric fields are their electric fields are parallel parallel

Note: This is different from Note: This is different from electrical polarization electrical polarization (sticking a balloon to the (sticking a balloon to the wall)wall)

Light PolarizationLight Polarization

Light Polarization

• Lightbulb – Nonpolarized• Projector – Split polarized• Monitor – Polarized

CCoolloor r Making Making ActivityActivity4/24/144/24/14

Objective:Objective:

To explore the properties of To explore the properties of light and color.light and color.

Materials:Materials:

Color MakerColor Maker White ScreenWhite Screen Multi-colored Screens (Red, Multi-colored Screens (Red,

Green, Blue and Orange)Green, Blue and Orange)

Pre-Lab Questions:Pre-Lab Questions: (Just (Just answer the questions.)answer the questions.)

1) List the colors of the visible 1) List the colors of the visible spectrum.spectrum.

2) Is it possible to make white 2) Is it possible to make white light by using only colored light by using only colored light? Explain why you think light? Explain why you think this.this.

3) What color do you think we 3) What color do you think we will get if we mix red and will get if we mix red and green light on a white screen?green light on a white screen?

Pre-Lab Questions: Pre-Lab Questions: (Write (Write the questions and answer the questions and answer them.)them.) 4) What color do you think we will 4) What color do you think we will

get if we mix red, green and get if we mix red, green and blue light on a white screen?blue light on a white screen?

5) Why do you think a banana 5) Why do you think a banana looks yellow to us in the looks yellow to us in the sunlight?sunlight?

6) What color do you think an 6) What color do you think an orange would look like in blue orange would look like in blue light? light?