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Bellwork (4/22) • What is interference? • The result of the superposition of two or more waves
Waves Demos and Notes 4/22/14
Mechanical Waves • The energy of the wave travels through the medium • The medium itself stays in the same location
Mechanical Waves • Slinky • Seismic (Earthquakes) • Water ripples (Surface waves) • Ocean Waves • Sound • String or rope
Mechanical vs. EM waves • Mech. Waves NEED a medium to travel through • EM Waves don’t need a medium • Mech. Longitudinal waves can propagate in fluids and solids • Mech. Transverse waves can propagate only in solids
Bellwork (4/24) • What is the physics concept behind 3-D movies? • Light Polarization
Today’s Agenda • Finish the Activity • Go over notes from Yesterday’s Activity • Start the next lab
Properties of Light 4/24/14
Part III: Polarization Film 1) 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?
Bellwork • What is the physics concept behind 3-D movies? • Light Polarization
Today’s Agenda • Notes from Yesterday’s Activity • Start the next lab
Properties of Light 4/24/14
Light and Color Pre-Quiz • Light is a mechanical wave. • All objects emit EM waves. • Light is a particle. • White light is the absence of colors. • Only light has photons.
Light and Color Pre-Quiz • Light travels slower in glass then air. • All colors of visible light have the same wavelength. • Radio waves and sound waves are the same type of wave. • Our minds are capable of filling in information that is not there. • The oceans makes our sky appear blue.
Light and Color Pre-Quiz 1. Light is a mechanical wave. False 2. All objects emit EM waves. True 3. Light is a particle. Somewhat True 4. White light is the absence of colors. False
Light and Color Pre-Quiz 5. Only light has photons. False 6. Light travels slower in glass then air. True 7. All colors of visible light have the same wavelength. False
Light and Color Pre-Quiz 8. Radio waves and sound waves are the same type of wave. False 9. Our minds are capable of filling in information that is not there. True 10. The oceans makes our sky appear blue. False
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 Spot • Focus on the text or a single letter • Move the closer and farther from you until the black dot disappears
What is Light? • Light:is range of EM radiation that can be detected by the human eye.
The Photon • Photon: A wave packet (quantum) of an EM radiation (ex. radio, light) • Travel at the speed of light • Have energy • Considered to be both a particle and a wave !
Light Transmission • Transmission – the process of EM waves passing through a material
Light Transmission • The energy of light transfers energy (vibrations) to electrons • Transparent materials have electrons in the material that match the frequencies of the light (E&M wave) • These photons reemit the light through the material
Light Transmission • Light (EM waves) will be absorbed (into heat) if the frequencies do not match. • (page 410)
Light Transmission • Transparent: The physical property of allowing EM waves to reemit (pass) through a material • Translucent: Allows diffused EM waves to pass through the material • Opaque: Does not allow EM waves to pass through
Light Transmission • Plastic film (transparent) • Grocery bag (translucent) • Printer paper (translucent) • Construction paper (opaque) • Black Plastic (opaque) • Aluminum foil (opaque)
Light Reflection • Reflection - The turning back of EM waves at a surface.
Light Reflection • Metals have free electrons to vibrate and reemit the light • Other materials absorb most of the light without much remission
Types of Reflections • Specular reflections – reflect the light in the same forward parallel direction (mirrors) • Diffuse reflections – reflect the light in many different directions (non glossy paper)
Light Reflection • Black plastic (mostly specular) • Aluminum foil (somewhat specular) • Plastic film (somewhat specular) • Grocery bag (diffused) • Printer paper (diffused) • Construction paper (diffused)
“How do we see objects?” • Light has to be emitted from a source • Light is absorbed / transmitted by the object • Light then is reemitted from the object • This is what we see!
Light Polarization • Light Polarization: The alignment of EM waves where their electric fields are parallel • Note: This is different from electrical polarization (sticking a balloon to the wall)
Light Polarization • Lightbulb – Nonpolarized • Projector – Split polarized • Monitor – Polarized
Color Making Activity 4/24/14
Objective: • To explore the properties of light and color.
Materials: • Color Maker • White Screen • Multi-colored Screens (Red, Green, Blue and Orange)
Pre-Lab Questions:(Just answer the questions.) 1) List the colors of the visible spectrum. 2) Is it possible to make white light by using only colored light? Explain why you think this. 3) What color do you think we will get if we mix red and green light on a white screen?
Pre-Lab Questions: (Write the questions and answer them.) 4) What color do you think we will get if we mix red, green and blue light on a white screen? 5) Why do you think a banana looks yellow to us in the sunlight? 6) What color do you think an orange would look like in blue light?