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An Activity-Centered General Science Course Concerning Light and Optics

Jeff Marx, Shabbir Mian, Vasilis Pagonis

Physics Department, McDaniel College, Westminster, MD

Each year in the United States hundreds of thousands of undergraduates enroll in introductory science coursesgeared towards non-science majors.1 As is the case at McDaniel College, these general science courses may be one of, perhaps,only two college-level courses in science or mathematics in which these students will participate. Unfortunately, we notice many students have poor math and science backgrounds, as well as a weak set of epistemological beliefs. We believe these weaknesses can negatively impact students' capacity to comprehend fundamental physical concepts and basic relations.

Faced with these concerns, we created a general science course covering light in which non-science majors engage in simple activities designed to help them understand basic light phenomena, while gaining a sense of their own capacity to investigate and logically postulate about the physical world. To accomplish this, we fused together several successful pedagogical techniques and environments introduced by the physics education research community over the past decade. Specifically, we coupled thePrediction-Experiment-Result routine of Interactive Lecture Demonstrations2 with the more intimate settings of Tutorials3and the hands-on Workshop Physics.4

In our course, A World of Light and Color, students regularly face their individual notions of various opticalphenomena by making intellectual commitments to their ideas by predicting, sometimes publicly, conceivable outcomes for a particular activity. Students then observe the phenomena and acknowledge any discrepancies between their ideas and the outcome by articulating and recording their observations. Finally, the class tries to establish the natural rules governing the phenomena under investigation.


McDaniel College is a selective, four-year, residential, liberal arts college, with an undergraduate population of about 1600 students. McDaniel's curriculum has a core set of Basic Liberal Arts Requirements. One of those requirements dictates that students pass two courses relating to the natural sciences and mathematics. For several years the Physics Department delivered A World of Light and Color, a single-semester, general science course at the 1000-level. Looking to improve the quality of this course, were modeled its structure into the form described in this paper. We offered the improved version for the last two years in eight different sections. Enrollment varied from eleven to twenty-four students, and 75% to 100% of the students in any given class were non-science majors.

Classroom Environment and Course Structure

The classroom has six large, low, rectangulartables with ample room to accommodate four students and equipment and materials used for any particular day. Students work in groups for nearly every step of each activity.

Whenever the class begins a new topic (roughly every other class meeting) the students must arrive at class with a completed Preparatory Sheet. Preparatory Sheets have the reading assignment for the day, as well as questions about basic properties of light germane to that topic. The answers to the questions are not in the text; rather, the students must rely on their own understanding (including what they gleaned from the reading) of the phenomena inquestion to arrive at their conclusions. We collect, grade, and return the Preparatory Sheets by the next class. The grading scheme is a scale from 0 (no work) to 3 (serious effort and coherent, but not necessarily correct, set of answers). The main function of the Preparatory Sheets is to force students to consider the material before coming to class.

As class gets under way, the students read the opening remarks on the Procedure and Results Sheet (PRS). Each PRS begins with a checklist of materials the students will use for that set of activities, as well as remarks concerning how to use any equipment safely and properly.

Next, the PRS directs students to their Prediction Sheet (PS) to begin the three segments of the Prediction Phase. The PS describes the activity the students will conduct; however, before they perform that activity, the students enter the first segment of the Prediction Phase by making a personal prediction as to the outcome of the activity by writing (or, more typically, drawing) their thoughts on the PS. We encourage students to make predictions on their own before they move on to the next segment when they discuss and debate their predictions with their partner(s)and table mates. Students are free to update their predictions based on the discussions. During the first two segments of the Prediction Phase the instructor moves around the room to look at various predictions and hold dialogues with individual students regarding their predictions. When the discussions subside, the instructor moves the class into the last segment of the Prediction Phase by eliciting several predictions from the class. These public predictions are voluntary or brought forth by calling on students. (Varying classroom dynamics and levels of difficulty require both techniques.) To encourage students to offer predictions, we do not require them to necessarily present their own predictions; rather, they can say what someone else at their table thought was reasonable. If feasible, the instructor draws, or writes, predications on the whiteboard at the front of the classroom so the students can appreciate the, sometimes wide, range of notions. Usually the students will engage in some discussion and non-confrontational criticism of the various predictions.

Once the Prediction Phase winds down, the class moves to the Observation Phase. At this point pairs of students perform the short activity described on the PRS to find out what really happens. Then the instructor carefully outlines the results on the whiteboard or demonstrates the phenomena to the entire class. Short discussions often follow while the students describe and/or illustratetheir observations on their PRS.

After a few cycles of Prediction and Observation we enter the Discussion Phase. Questions or ideas for discussion are on the PRS. These discussion questions give the students the chance to bring the last few observations together under one physical principle. We have students discuss the observations and possible overarching explanations with their table mates, first. Then the instructor holds a short class-wide discussion to get the various opinions and explanations out in the open. Hopefully, the class will come to some correct consensus about the broader physical idea. If they do, then the instructor simply restates the consensus, sometimes with more compact verbiage, so everyone has a chance to write down the major ideas on their PRS. If the class can not see the broad concept, then the instructor faces the challenge of bringing the class around to the correct idea while avoiding simply telling them what to think. Since we have carefully chosen our topics and observations, the latter situation rarely arises.

The entire class hour is filled with this cycle of Prediction-Observation-Discussion. Several topics span more than one class meeting to help ensure the students have a firm grasp of the material. (Classes meet three times per week.) The students do not take notes as they would in a more typical class. The information they compile on their PRS serve as the notes for the class. Other aspects of the course are more traditional. The students complete ten homework assignments (with short-answer questions and numerical problems), three short quizzes and three hour-long exams, and a comprehensive final.

Topics and Activity Examples

The outline of topics we cover in our class is located in Table 1. The reader familiar with this type ofcourse will recognize the topics as part of the standard set for a course of this type.

Table 1: Topics covered in A World of Light and Color


classes devoted

Basic Properties of Light

Relationship Between Color and Wavelength


Light Beyond the Visible: IR and UV


Reflection, Absorption, and Transmission


Relationship Between Intensity and Distance


Color Mixing: Addition and Subtraction





Ray Reflection from a Plane Mirror


Image Formation by a Planar Mirror


Ray Reflection from a Curved Mirror


Image Formation by Curved Mirrors




Total Internal Reflection


Fiber Optics


Ray Refraction by a Lens


Image Formation by Lenses


Telescopes and Cameras


Pinhole Camera


Physical Opticsand Polarization

Reflection and Superposition of Waves


Water Waves in the Ripple Tank




Two-slit Interference





Eye, Mineral Identification, Relativity.

3 or 4

To expose the students to the various topics,we developed a diverse set of activities. For example, to understand shadows, the students use a floodlight to cast the shadow of a small cylindrical object on a white screen. The students discuss and develop models for the light ray paths for various source-object configurations and develop an understanding of the various shadows' shades and shapes.Building on this, the students think about the details of the object's shadow when the source shines through a small hole in an opaque screenand when the source is behind a sheet of white paper. They also observe shadows cast by multiple sources, paying close attention to the varying shades of gray for each shadow. Finally, the students combine what they learned about color addition in previous activities and their new knowledge about shadows and multiple sources to predict and observe colored shadows.

To help students understand how a pinhole camera functions, we developed an activity in which the student plays the role of the film in a pinhole camera. The students place the object (paper with bold symbols printed on it) about 50 cm from a piece of cardboard with a small hole punched in it, which is fixed to one side of a 10-gallon aquarium. At the other side of the tank, the students attach a transparency sheet. (See Figure 1.) Students carefully line up a marker with the tiny part of the object they see through the hole and then mark a dot on the transparency. By repeating this for many locations, a pattern emerges on the transparency that resembles the object. By looking at the transparency from the inside of the tank, the students see what the pinhole image looks like. This activity reveals how the pinhole enforces a particular one-to-one relationship between locations on the object and on the image. It also prepares students to make predictions regarding the relationship between the object distance and the size of the image. And, it helps them understand why the pinhole image is inverted and reasonably sharp nearly independent of the object distance, which differs from the image created by a lens.

Figure 1: Set-up for the Pinhole Camera Activity

Set-up for the Pinhole Camera Activity

Reflections and Suggestions

Teaching a learner-centered course can be a challenge, as instructors must carefully balance their level of involvement. Too much intervention ruins the pedagogical intent; too little, and the class collapses into a frustrated heap. Along with aligning our course with the inspiring curricular materials we mentioned earlier, we worked hard to create activities in which the instructors can easily assume an engaging, but not overbearing, position. Along those lines, we present several observations we trust instructors may find useful when implementing this or similar courses.

First, we strive to keep a safe and open intellectual environment. If students sense the potential for ridicule, they will certainly not offer their predictions and ideas and may look to by-pass the critical Prediction Phase altogether. The instructor must carefully mediate interactions so there are thoughtful and polite evaluations of predictions and discussions. Since many ideas will be incorrect, in one form or another, it is important to highlight the fact that the entire class learns together and that even incorrect notions help everyone. All of this begins with the instructor who must serve as a model of how to deal with multiple notions of the physical world by rewarding honesty and openness.

Second, when students make and recordobservations, it is often important to discuss the ideal result fromthe actual result. For example, the color addition and subtractionexperiments often yield results that differ from what one would predictusing an ideal filter model. This mismatch can frustrate students, but we turn that around and use the discrepancy to point out that models have limitations and once one understands those limits, useful predications are still possible. Also, we make sure every student correctly records observations on their PRS. Frequently, all the students are looking same thing, but a few may interpret what they see differently than everyone else. For example, when students view colors projected onto a white screen, they sometimes mistake colors they observe as a result of the influences of nearby colors on the samescreen.

Third, we feel preparatory work is an essential part of the type of learning environment we are attempting to create. Unfortunately, we have found it difficult to craft effective Preparatory Sheets for all of the topics. Because we want to encourage students, we tended to err on the side of caution and write relatively easy Preparatory Sheets. However, a bolder approach may be appropriate.

Also, we tried to make certain that each cycle of prediction, observation, and discussion focused on one concept. Moreover, we focused each class on one or two robust optical principles. We wanted students to come away from each class with broad concepts, not a bunch of notes on specific and seemingly disconnected examples. This serves to reinforce the idea that scientists often look for "Big Thoughts" that tie hosts of observations together.

Finally, for the vast majority of activities we intentionally avoided observations and experimental set-ups that require electronic interfaces. We recognize the important role technology plays in science, and we certainly would like our students to appreciate that, too. However, we felt it was more important for our students to feel a strong sense of ownership of their observations. Our population lacks both an understanding of physical phenomena and experience using computers and electronic equipment as experimental apparatus. We felt this presented too many pedagogical barriers, so we cleaved to a low-tech approach.


We have developed materials for our optics course, A World of Light and Color. We based the course's curriculum on techniques previously established to help students come to a full understanding of basic physical concepts. In particular,students proceed through a cycle of prediction, observation, and discussion to help them relate to fundamental ideas concerning light. We encourage instructors to contact us for more information.


This project was funded by the National Science Foundation under the CCLI program (award number 0125828).


1. Over 200,000 undergraduates enroll in introductory astronomy eachyear, alone. See Franknoi, A., "The State of Astronomy Education in theU.S.", Astronomical Society of the Pacific Conference Series,Vol. 89, edited by J. R. Percy, Astronomical Society of the Pacific,San Francisco, 1996, p. 9 - 25

2. David R. Sokoloff and Ronald K. Thornton,"Using Interactive Lecture Demonstrations to Create an Active LearningEnvironment", The Physics Teacher 35: 6, 340 (1997).

3. Lillian C. McDermott, Peter S. Shaffer and the Physics EducationGroup, Tutorials in Introductory Physics, (New Jersey,Prentice Hall, 1998)

4. Priscilla W. Laws and several contributingauthors, "Workshop Physics Activity Guide" (New York,Wiley, 1997).