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OPTICS and VISION Judy Donnelly Three Rivers Community College Nicholas Massa Springfield Technical Community College Fenna Hanes New England Board of Higher Education ASEE K12 2007 OPTICS and VISION TODAY’S AGENDA Introductions A little bit about light Color activities BREAK What do optical engineers do? Optics activities ASEE K12 2007 OPTICS and VISION A WORD FROM OUR SPONSOR… New England Board of Higher EducationProjects PHOTON, PHOTON2 and PHOTON PBL These activities are favorites of the teacher participants of the PHOTON projects: Middle school High School College- distance learning Teacher Professional Development ASEE K12 2007 What can you do with light?…. ASEE K12 2007 SO WHAT IS LIGHT? Nobody really knows! So, we just describe its behavior: Sometimes it acts like a wave Sometimes it acts like a particle Sometimes we can ignore both waves and particles and say it’s a “ray” that obeys geometric laws ASEE K12 2007 When we talk about light colors, we refer to the wavelength of the light. Wavelength is the distance from one peak to the next. Ocean waves have wavelengths around a meter or two. Bathtub ripples have wavelengths around a centimeter or two. What about light waves? ASEE K12 2007 Wavelengths of visible light waves are less than one micrometer (0.000001 m)! This is one micrometer! This is a hair. (about 80 micrometers in diameter) This is the wavelength of blue light (0.5 micrometer) ASEE K12 2007 Visible light is part of the Electromagnetic Spectrum The regions of the spectrum overlap somewhat. The visible portion is a very small part of the total spectrum! ASEE K12 2007 The Colors of the Visible Spectrum Red Orange Yellow Green Blue Violet Remember “Roy G. BV” ASEE K12 2007 Colors we can’t see are important to science and technology. Black-Eyed Susans in visible and ultraviolet light Cleopatra butterfly in visible and ultraviolet light From Alien Vision by Austin Richards SPIE Press, 2001 ASEE K12 2007 Colors we can’t see are important to science and technology. Infrared image from Boston University Center for Subsurface Sensing and Imaging Systems. The image is color-coded for easier interpretation. Why are the eyeglasses black? ASEE K12 2007 Light and matter When light encounters matter, it may be: Reflected Transmitted All of these may take place to some extent Absorbed Scattered ASEE K12 2007 Today’s 1. 2. 3. 4. experiments*: What Color is a…?- Seeing colors Spectroscopy- Colors of light sources Jello® Optics- Transmission and absorption The Mirror Game- The geometry of reflection These topics are addressed in the fifth grade science standards in Connecticut. ASEE K12 2007 #1: The Colors of “Things” THE CHALLENGE •What color is a tomato? •Why? •Can you change the color of a tomato? (no paint allowed!) THE MATERIALS •Color LEDs (or flashlight with color filters) •Pieces of colored candy or paper, fruit, etc HINT Darken room if possible. Object can be placed inside a deep carton if room lights can’t be turned off ASEE K12 2007 #1: The Colors of “Things” THE EXPLANATION The color you see depends on: •The wavelengths reflected by the object •The wavelengths present in the illumination •The color sensitivity of your eyes White Light Looks orange Blue Light Looks black ASEE K12 2007 Very Dim White Light No color vision! #1: The Colors of “Things” APPLICATION: Color science is important to display technology, paint matching, and retail illumination. Southern Cal Edison Lighting Showroom ASEE K12 2007 #2: The Colors of Light THE CHALLENGE •What colors are given off by a source of light? •Can you tell what colors are in a source of light just by looking at it? Yellow? ASEE K12 2007 #2: The Colors of Light THE MATERIALS: Building the “spectroscope” 1. To separate the light into its basic colors, you could use a prism (difficult!) or a diffraction grating 2. Recycling: use a CD with the label stripped off! (This is a type of diffraction grating.) 3. To block out other nearby light sources, use a short cardboard tube. 4. To separate the colors so they don’t overlap, use a slit. Light source slit tube ASEE K12 2007 CD “grating” look in here #2: The Colors of Light SAFETY HINT: •Don’t look at the sun or into a laser! THE EXPLANATION Different types of light use fundamentally different processes to create light. The colors seen depend on the type of source and the source materials (type of gas, semiconductor, etc.) • Heat (incandescent bulb) • Glowing gases (neon lights, sodium street lamps) • Fluorescent bulbs- the color is determined by the phosphor coating on the inside of the bulb • Light emitting diodes (LEDs) • Lasers ASEE K12 2007 #2: The Colors of Light APPLICATION Substances can be identified by the colors they give off when they are heated, or by the colors they absorb. 194 nm 284 nm 304 nm UV images of the sun from the SOHO web site http://sohowww.nascom.nasa.gov/ http://honolulu.hawaii.edu/distance/sci122/ ASEE K12 2007 ASEE K12 2007 #3: Jello® Optics THE CHALLENGE •How does a lens work? •How does an optical fiber work? THE MATERIALS •Jello® Jigglers (can be made with plain gelatin) •Stiff plastic or cookie cutters •Laser pointer or small focusable flashlight HINT Keep cut edges flat and smooth for best results. Clear plastic pieces are available from science supply companies if gelatin is too messy. ASEE K12 2007 #3: Jello® Optics SAFETY HINT: •Don’t look into the laser or shine it into anyone’ eyes! THE EXPLANATION •Light slows when it goes from air into the gelatin •The slowing leads to a bending of waves •Consider a marching band, going from pavement to mud… Mud "normal line" Paved ASEE K12 2007 #3: Jello® Optics THE EXPLANATION (With Math) • Snell’s Law: n1sinθ1 = n2sinθ2 • From air to gelatin: Bends toward the normal • From gelatin to air: Bends away from the normal θrefr θrefr θincc θinc n1 fast n2 slow n2 slow ASEE K12 2007 n1 fast #3: Jello® Optics APPLICATIONS • Lenses • Optical Fiber (Total Internal Reflection) ASEE K12 2007 #4: Hit the Target THE CHALLENGE •How does a mirror work? •How can you use a mirror to steer a light beam? THE MATERIALS •Plastic mirrors mounted on blocks •Laser pointer •Target •String, protractor, meter stick, tape HINT You don’t need to use all of the materials. Use what you think is most helpful. ASEE K12 2007 #4: Hit the Target SAFETY HINT: •Always know the location of the laser beam. Let everyone know when you are turning the laser on. THE EXPLANATION • Law of reflection: θincidence = θreflection θincidence θreflection ASEE K12 2007 #4: Hit the Target APPLICATION “Optical Levers” used to steer light beams ASEE K12 2007 Resources for teaching optics Web sites with information and activities www.nebhe.org www.opticsforkids.org www.opticsforteens.org www.hands-on-optics.org www.lasertechonline.org (links at bottom right) Free posters and career materials Available at www.spie.org and www.osa.org List of optics tutorials and Java/Flash applets http://www.lasertechonline.org/optics_links.html College and career information www.qcc.cuny.edu/physics/lfot/LFOT_FAQs.asp www.opticseducation.org/ ASEE K12 2007