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1.INTRODUCTION AND OBJECTIVEThe Optics Suitcase (see Figure 1) is an educational outreach tool developed by Dr. Stephen D. Jacobs and the OSA Rochester Section (OSA-RS) with the busy professional in mind. It is designed to make it easy to enter a middle school classroom and excite young people about careers in technology using experiments that can be customized to highlight the presenter’s interests, job and work environment. The Optics Suitcase contains both reusable and giveaway supplies (see Table 1). Table 1:List of Optics Suitcase reusable and giveaway supplies
The objective of the Optics Suitcase is to convey a sense of excitement about technology in a short period of time. To achieve this goal, the initial demonstrations serve as “ice breakers” and are intended to quickly capture the students’ attention. Next, three hands-on activities use the theme packets and illustrate the overall theme of “colors in white light”. They are presented as a pace best suited (as determined by the presenter) to retain the students’ interest, and children often enjoy taking the theme packets home and sharing with others. The presenter can customizing the template take-home flyer with a name, the date and the location of the presentation to help reinforce the message with the students. 2.PREPARING FOR A VISIT TO THE CLASSROOMOne to two weeks before the visit, it is recommended to obtain the following information from the classroom teacher to prepare the suitcase and make a take-home flyer:
The day before the visit, the presenter should check the contents of the suitcase. It is necessary to ensure that the heating demo pad is in its liquid phase (see Section 3), to print out the flyers (included a digital copy that can be projected as part of the presentation, and to find time to practice the presentation. 3.GETTING STARTED (BREAKING THE ICE)Presentation times are often limited to a class period (~45 minutes). It is very important to grab the students’ attention immediately and to maintain a quick pace for the entire presentation. After the teacher or one of the students has completed the introduction, start with two general science demos to help break the ice. 3.1.Heating Pad DemoPick a student from the class and ask him/her to help with the first experiment. Hold up the heat pad without indicating what it is and hand it to the student. Ask him/her to gently handle the heat pad and describe how it looks and feels (squishy, transparent, liquid, and cool to the touch). The student may need to be gently prompted to get these answers. Ask the student to hold up the heating pad so that everyone can see it, allowing the metal disk inside the pad to sink to the bottom of the pad. Help the student to snap the metal disk to initiate crystallization. Describe how the crystallization, accompanied by heat, spreads throughout the pad in approximately 30 seconds. The pad turns opaque. Prompt the child to describe the pad, now that it has become hard and hot! Pass the heating pad around, so that everyone can feel the heat, while providing additional information:
Put the heating pad back into the Optics Suitcase. 3.2.Happy and Unhappy BallsSelect two students to help with the next experiment. Give each student a rubber ball and ask them if the balls look and feel the same. (The answer is “yes”.) Ask each student to bounce his/her ball in a location where others can see the zone of contact between the ball and hard surface (desktop, wall or floor). One ball will bounce; the other will not. Explain that this demonstration is an example of polymer and materials science.
Questions for the students might be: What is a good rubber for the bumper on a car? What rubber would be best for a handball, or the soles of a pair of sneakers? This is a good time to point out that technology and innovation are the keys to improving our lives. Put the demo can then be put back into the Suitcase. 4.INTRODUCTION TO OPTICAL ENGINEERINGOnce the students’ attention has been captured, it is time to introduce the field of technology called “Optical Engineering”. Hold up the silicon wafer (shiny side out) and the silica glass lens (see Figure 2). Ask if anyone can identify these “optics”. The lens is usually easily recognized and described. The students will likely refer to the wafer as a mirror. Identify the wafer as single-crystal silicon, a pure elemental substance and the basis for all computers (the chips and microcircuits). Show the students the reverse side of the wafer, which is dull, and explain that this side is ground and the other is polished to a mirror surface. Some optical engineers develop the technologies for turning rough silicon wafers into integrated circuits for making computer chips. You may want to elaborate on this. Hand out copies of the periodic table of elements (useful for 8-9th grade and higher). State that the periodic table is a visual means for displaying all of the elements known to man - every bit of matter in the universe is composed of one or more of these elements. Ceramics engineers, chemists, materials scientists, geologists, and optical engineers work with many of these elements and the compounds they form. Explain that the only difference between the silicon wafer and the silica lens is oxygen. Help the students locate silicon (#14) and oxygen (#8). Point out that the addition of oxygen turns a visibly opaque material into a visibly clear one. Suggest that if we were aliens whose vision was in the infrared, the silica lens would look opaque and the silicon wafer would look transparent! Note that many insects have infrared vision. Mention that optical engineers build lenses into systems that image light, such as the Hubble Space Telescope, the Chandra X-ray Telescope, digital cameras and smart phones. 5.COLORS IN WHITE LIGHTOnce the students are engaged and have had a brief introduction to Optical Engineering, conduct three experiments that illustrate optical engineering. These experiments explore several ways to “see” the colors in white light. The demos can be described as revealing “secrets” that might not be obvious to others when doing the experiments. The “trick” or “secret” aspect to the demos often works well to continue to engage students. This is a good time to project an image of the take-home flyer (see Figure 3) that describes optics and what it takes to be successful in this career. They flyer can be passed out at this time or at the end of the presentation as a summary. The three experiments that the students will perform are: the Rainbow Peephole (color by diffraction), the Magic Stripes (color by polarized transmission) and the Magic Patch (color by selective reflection). 5.1Rainbow Peephole (Color by Diffraction)Distribute the Rainbow Peephole theme packets (see Figure 4a), but ask the students to not open them yet. When everyone has their own packet, remove all of the items from the packet, hold them up and identify them. Direct the students to remove the contents from their packet. Hold the peephole up to your eye and look at the flashlight through it. Ask the students to do the same. During the “oohs” and “ahs,” ask the group, “Where does the color come from?” Many children will answer that the colors come from the peephole. Tell them that the color comes from the white light in the flashlight. There are several follow-up questions that can be asked. Do you see a regular pattern? Describe it. Identify all of the colors. Are they the same in each spot? Does the pattern change if the flashlight is close or far away? Do you see colors from other people’s flashlights, even those far away from you? Do you see colors from the room lights? Are colors and patterns from all light sources the same? The image on the packet has an atomic force microscope (AFM) image of one side of the clear plastic in the peephole. This is a good opportunity to mention that the AFM is a tool often used by engineers to help see objects at high magnifications. The scale on the image is in microns, which may not be a unit of measure the students are familiar. It can be noted that a human hair is 30 to 80 microns wide, and the bumps across the peephole are only two microns high, which is too small to be seen or felt. The bumps are packed so closely together that about fifty could fit inside a human hair. These bumps are responsible for breaking up the light coming into the peephole. This effect is called “diffraction”. It occurs when light travels through small apertures (e.g., holes or slits). Point out the similarity between the regular array of bumps and the pattern seen though the peephole. A great application example is telecommunications. Ask for a show of hand of everyone that has or wants a cell phone. Using the slide shown in Figure 4b, explain how telecommunications use fibers and lasers to divide light from one beam into many, each with a different color. It can be explained that this is the key to unlimited number of conversations all over the world at the same time. At this time, ask the students to put the Rainbow Peephole experiment away and tell them that the packets are theirs to keep. Remind them to reveal the secret of seeing colors in white light through diffraction to family members. 5.2Magic Stripes (Color by polarized transmission)To start the next experiment, choose a volunteer to come to the front of the room. Give the student one end of the slinky and ask her/him to hold their end steady and mid-chest level. The presenter should stand approximately four feet away and begin to shake the slinky randomly: up and down and in a circle. The presenter should be able to create a standing wave with a few nodes, but the plane of vibration should not be well defined. State that, in addition to color, light has a wave nature. The slinky represents a light wave. The motion represents unpolarized light, or light without a preferred vibration direction. For simplicity, it is recommended to ignore circularly polarized light. At this point, stop the circular motion and vibrate only vertically. The presenter should state that light is “polarized” when it vibrates in one direction, vertical or horizontal. While explaining, switch to a horizontal hand motion. The horizontal motion is a bit harder to maintain while speaking, so switch back to vertical motion, if necessary. Define linearly polarized light as light that vibrates in a plane. The NASA slide (see Figure 5) showing the spectrum from radio to gamma rays is an additional way to introduce different wavelengths of radiation. The lower photos show how the Milky Way looks when viewed through different telescopes that “see” at various wavelengths of optical radiation. At this point the Magic Stripes theme packets (see Figure 6a) can be handed out, and again, instruct the students not to open them until everyone has received a packet. Take the two larger pieces of linear sheet polarizer and holds them up, one in each hand. Placing the combined pieces in front of the presenters face allows the students to see the transmission when the axis are parallel and then crossed after rotation. Ask students to remove everything from the packet and place the items on their workspace. Tell the students that the sheets of plastic are called “polarizers” that only allow light vibrating in one direction to pass through and therefore rotating the polarizers in opposite directions prevents any light from passing through. Now they can try to perform the same experiment with their two smaller linear sheet polarizer from their packets. Mention that polarized sunglasses are an example of a commercial application. If there is an overhead projector in the room, darken the room. Create and project a polariscope by placing one polarizer directly on the light bulb, positioning four plastic cups on the corners of the polarizer, and placing the second polarizer on top of the cups. Place clear plastic silverware included in the Optics Suitcase in the polariscope. Students are typically very excited about what they see. Ask the students where the color comes from. At this point in the presentation, there might be some correct responses. If someone has glasses, ask them to place them in the polariscope. Explain that the stresses inside transparent materials degrade the quality of the linearly polarized light coming through the polariscope and cause various colors to show up. Careers and applications that use polarizers include geologists identifying certain crystals and mineral structures or optics technicians evaluating the quality of laser glasses and laser crystals. With the room lights back on, show the students how to create their own polariscope with the items in their packet. The polariscope can be held in one hand and the clear plastic items can be placed between the crossed polarizers in the other hand. The students can look through the crossed polarizer “sandwich” at the overhead lights. The slide shown in Figure 6b can be projected to show the students the experimental procedure and also to indicate that the colors they are seeing indicate how much stress (optical retardance) is present in the transparent material. The students can apply additional stress on the tongs of the fork and see the effects in their handheld polarizer. As the students are asked to put the Magic Stripes theme packet away, suggest that the students demonstrate the Magic Stripes to trick their families, since they now know the secret polarizer code and how to construct a polariscope. 5.3Magic Patch (Color by selective reflection)Before starting the third experiment, remind the students that he/she has demonstrated how to see colors in white light through diffraction and polarized transmission. While all the students are watching, take the large sheet of microencapsulated liquid crystal and place it in front of a volunteer’s face (glasses off, if they wear them), shiny side out. Ask where the colors are coming from. If students guess the heat comes from the presenter’s face, respond no. Explain that the colors come from the white room lights reflecting off the black “paper”. As the teacher passes out the Magic Patch theme packets (see Figure 7a), explain that the paper has a liquid crystal fluid trapped, or encapsulated, against the shiny side. At the right temperature (84 - 91°F), the liquid crystal droplets reflect selective colors of white light. When the liquid crystal sheet is cold there is no reflection (of visible light) and the sheet appears black. When the liquid crystal start to warm, they start to reflect red light. If they warm up sufficiently, they will reflect deep blue light. This effect is called selective reflection. The slide included on the USB stick can be used to compare liquid crystal molecules to springs. Commercial applications that students may be familiar with are “mood rings” or fish tank thermometers. Included on the USB is a slide showing a potential medical application that also gives a subtle message about smoking (see Figure 7b). Once all of the students have their Magic Patch theme packets, instruct them to take their patch out of the bag and perform the vampire test by placing the patch on their wrist. Vampires are the living dead, and give off no heat. The presenter will ask if anyone can “see” a vein. The effect is reversible. As students put the Magic Patches away, remind them that liquid crystals are found in everything from cell phones to watches to laptop computers to video games. It allows an additional opportunity to reinforce the importance of engineers and scientists to develop the technology we all use every day. 6.SUGGESTIONS AND TIPSAfter giving dozens of presentations, Steve Jacobs and other members of the OSA Rochester Section learned quite a few lessons. A few general observations and suggestions are provided:
7.ACKNOWLEDGEMENTSDeveloped by the OSA Rochester Section (OSA-RS) in 1999, the Optics Suitcase is an innovative, interactive presentation package designed to introduce middle school students to the dynamic and exciting range of concepts within the study of light. To request an Optics Suitcase, please visit us online at www.osarochester.org Funding for this program comes from many sources. We would like to acknowledge the OSA Rochester Section, the Laboratory for Laser Energetics (LLE) of the University of Rochester, Masline Electronics Inc. and the OSA Foundation for major support. Dr. Stephen D. Jacobs made lasting contributions to the fields of optical materials, liquid crystals, and optics manufacturing, but it is his passion for educational outreach which continues to impact countless young (and older) lives. He spent his entire career at the University of Rochester with appointments at the Laboratory for Laser Energetics (LLE), Institute of Optics, Materials Science and Chemical Engineering departments. He volunteered as the educational outreach chair for the OSA-Rochester Section for over 15 years during which time he developed and organized the Optics Suitcase program that has been instrumental in introducing hundreds of thousands of young children to the fields of optics and materials science throughout the US and globally. REFERENCES:Reference Optics Suitcase Guide found at website,”
https://www.osarochester.org/resources/Documents/EducOutreach/OSA_OpticsSuitcaseGuide_020718[19509].pdf Google Scholar
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