50 Science and Children

Circusof Light

By Juanita Jo Matkins andJacqueline McDonnough

A science circus shines the

spotlight on light with a fun and

efficient way to include more

science activities in a lesson.

Imagine a classroom containing severalsmall groups of students engaged invarious science activities at stationsaround the room. At regular intervals,the groups move to another station.After about 45 minutes the children

have worked at all the stations and return totheir desks, discussing the questions posed atthe different stations. The teacher then leadsthe class in a discussion about the science topic,using the experiences at the stations to guidethe students to understandings about the topic.This class just performed a “science circus.”

50 Science and Children

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A science circus is a set of activities done in any orderthat together illustrate complementary properties of ascience topic. As in a traditional circus, several “perfor-mances” occur at the same time, and students focustheir attention on one activity while others are going onsimultaneously. Similar to the ringmaster of a circus,the teacher guides and directs students as they circulatethrough the stations.

In this article, we describe the light-based sciencecircus we developed and tested with a fifth-grade classat Blackwell Elementary School in Richmond, Virginia.

Why Do a Science Circus?Many science topics are complex, and two or threeactivities are often insufficient to support student con-cept development. How can teachers fit more activitieson a topic into the classroom schedule? Our answer wasto alter the pattern of doing science activities in se-quence and instead do several at the same time. Withthe time saved we had more time to lead discussions

with the entire class, helping construct understandingsabout the topic.

There are three steps to a science circus on any topic:(1) the hook, a question that generates student interest inthe topic; (2) the activities that explore that question andother aspects of the topic; and (3) the forum, the teacher-led class discussion of the topic.

For our study of light, our hook was a thought-provoking question related to a misconception manychildren and adults have about being able to see anobject even though there is no light shining on theobject: “If you were in a completely dark room,would you be able to see anything?” The studentswere divided over the answer. Several insisted youcould see in complete darkness, while others arguedyou had to have some light. We led them to thesecond step of the circus by explaining we were goingto do some activities that might show them the an-swer to that question. The science circus activitiesare described in Figure 1 on page 52.

We planned our five circus activities—“BouncingLight,” “Bending Light,” “Light in the Darkness,” “Meand My Shadow,” and “Making a Rainbow”—by firstidentifying the basic understandings about light wewanted to introduce to students. These understandingsare consistent with the National Science EducationStandards on light (NRC 1996). We wanted the stu-dents to explore the following ideas:

• Light travels in a straight line;• The angle of incidence of light striking a reflecting

surface is equal to the angle of reflection;• Light is necessary for us to see;• Light refracts or bends when it passes through

substances of different densities as it travels to oureyes; and

• Visible light has all the colors of the rainbow in it.

Directions were posted at each station, as were ques-tions to be answered in the students’ science logs. Thestudent teams had seven minutes at each station, andwe gave students extra time to finish their written re-sponses once all activities were done. Students wereencouraged to discuss their observations with theteacher and their classmates throughout the circus.

The ForumWhen students have completed the circus activities,it’s time to discuss what students discovered in theforum. During the circus we paid close attention towhat students were saying to each other, and wenoted what students were saying about each activity.We used this information to guide our questionsduring the forum.

52 Science and Children

Bouncing Light..... We set up the materials for this sta-tion—————a flashlight, a tennis ball, a large mirror, and apowder puff with some talcum powder on it—————in a darkcorner of the classroom with enough space for studentsto bounce a ball back and forth.Do and Discuss

1. Bounce the ball at different angles. Compare theangle of the ball’s path as it approaches the floorwith the angle of its path as it leaves the floor.

2. Place the mirror face up on the floor and“bounce” the light beam from the flashlight offthe mirror, then at different angles. Shake thepowder puff over the light beam to help you seethe path of the light.

3. Compare the angles of the light beam ap-proaching and leaving the mirror.

Science Log Questions1. Draw pictures of the path the ball takes to and

from the floor.2. Draw pictures of the paths the light beam takes

to and from the mirror.3. How do the angles of the light beam approach-

ing and leaving the mirror compare with theangles of the bouncing ball approaching andleaving the floor?

Bending Light..... At this station, students observed apencil in an empty glass and in a glass of water.Do and Discuss

1. Place the pencil in the empty glass. Look at thepencil from the top and the side. Predict whatthe pencil will look like in the glass of water.

2. Put the pencil in the glass of water. Look at thepencil from the top and the side.

Science Log Questions1. Draw what the pencil looks like in the empty

glass and in the glass of water. What appearsto happen to the pencil?

2. What ideas do you have about this effect? (Hint:Think about how water is different than air?)

Light in the Darkness..... For this station, we placed alarge cardboard box on its side on a table and draped asheet over it (to make it completely dark inside). Inside,we placed a flashlight, a mirror, a piece of white paper,and a small object (a toy cow).Do and Discuss

1. Put your head in the box and cover up with thesheet. Can you see the object?

2. Shine the flashlight on the object. What do yousee now?

3. Predict whether you can see the object without

shining the flashlight straight at it.4. Aim the flashlight behind you. Can you see the

object?5. Hold the mirror out beside you and aim the

flashlight at the mirror. What do you see now?6. Hold the piece of paper out beside you and aim

the flashlight at it. What do you see now?Science Log Questions

1. What were the sources of light in this activity?2. Were you able to see the object when you shined

the flashlight behind you? How about when youused the mirror and the piece of paper?

3. Which way was it easiest to see the object? Why?4. Draw the direction the light energy travels

when you can see the object. Include the lightsource, the object, your eye, and anything elseyou think helped you see the object.

Me and My Shadow. . . . . This activity requires a fairly darkarea, a light source (such as an overhead projector or alamp), a screen or blank wall, and a set of pictures ofshadow creatures (shapes) to form with their hands,such as a bird, a dog, and an elephant.Do and Discuss

1. Hold your hand in front of the light and observewhat happens.

2. Remove a shadow creature card from the bag.(Don’t tell what it is.) Take turns with yourteammates making the shadows. Guess whatthe others are making.

3. Can you make your shadow creature grow big-ger? Smaller?

Science Log Questions1. Sketch your idea of the path the light traveled.2. Why do you think the size of the shadow

changed when you moved your hands?

Making a Rainbow..... At this station, we set two prismsnext to the teacher’s overhead projector.Do and Discuss

1. Hold one prism in the path of the light comingfrom the projector and find the rainbow. Deter-mine where the light emerges from the prism.

2. Hold the second prism in the path of lightcoming out of the first prism. See if you canposition the second prism so the rainbow be-comes white light again.

Science Log Questions1. Draw the path of light going into and out of the

prism. What happens in the first prism thatmakes the rainbow appear?

2. Draw your idea of what happens when you usethe second prism to make the light white again.

Figure 1.

Five-ring science.

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February 2004 53

We wanted students to construct thescientific ideas for themselves, with only alittle guidance from us. We had alreadyplanned to use certain questions to guidethe forum discussion, and we added ques-tions inspired by student interactions.

The questions were all intended toguide the students into realizing howeach activity related to the specific char-acteristic of light it was helping to dem-onstrate. Because all of the students hadcompleted each activity, they were ableto draw upon on their own observationsand experiences as a foundation for dis-cussion and for the development ofconcept understanding about the topic.What follows is how the light discus-sion progressed.

Light travels in a straight line.We began by discussing the “Bouncing Light” activity,asking “Did the light from the flashlight travel ‘everywhich way’?” Students commented that they had ob-served the light traveling in a straight line from theflashlight and talked about using the powder puff andmirror to see the path the light took when it left theflashlight.

Next, we discussed “Me and My Shadow” by ask-ing, “What did you do to make the shadow larger?”Students commented that the shadows got biggerwhen they held the creatures (their hands) closer tothe light source. “Why do you think that happens?Could it have anything to do with the path light trav-els?” One child suggested, “The closer to the light thatyou hold the shadow creature, the more light youblock. That’s why the shadow gets bigger. The light istraveling in a straight line and it’s blocked by theshadow creature—it can’t go around.” The classagreed with the comment, and we then asked, “Do youall feel okay about making a rule about the way lighttravels through the air?” The entire class agreed “lighttravels in a straight line” was a good rule.

The angle of incidence is equal to the angle ofreflection.We asked, “In the ‘Bouncing Light’ activity, what hap-pened to the light when it left the mirror?” In previousclasses, students had learned about acute (less than 90degrees) and obtuse (greater than 90 degrees) angles. Inthis activity, students observed that when light traveledto the mirror at an obtuse angle, it came out at an obtuseangle, and that when light traveled to the mirror at anacute angle, it came out at an acute angle.

When asked, the class was unanimous in agreeing

that the angle going in was the same as the angle of lightcoming out. We explained that the angle going in wascalled the angle of incidence and the angle going outwas called the angle of reflection. We put the newvocabulary into their previously agreed-upon obser-vation about the angles being equal. They agreed that“the angle of incidence is equal to the angle of reflec-tion” was a good rule for light reflecting off a mirror.

Light is necessary for us to see.Did the students remember our “hook” question, “Ifyou were in a completely dark room would you beable to see anything?” What did they think now?They agreed that they had to have the flashlight on tosee the toy cow in the box. We asked, “Where did thelight start, and how did the image get to our eyes?”We drew an eye, a flashlight, and a cow on the board,and asked the class how we might draw arrows toshow how light helped us see (Figure 2). The stu-dents said the light started with the flashlight. Somethought light went to the eyes next, and some thoughtlight went to the object.

We explained we see things because light strikesthose things and that light, or part of it, is reflected intoour eyes. It is the light entering our eyes that sends thesignal to our brain about the appearance of the object.With our human senses, we cannot tell when lightleaves a source and hits an object and is then reflectedto our eyes. It’s just too fast.

Light bends, or refracts, when it passes throughmore than one substance as it travels to our eyes.“What about the pencil in the glass of water (‘BendingLight’)?” we asked, “Does the pencil look different in

Figure 2.

Pathways of light diagram.

Flashlight

Path of light fromsource to object

Path of light fromobject to eye

54 Science and Children

Connecting to the StandardsThis article addresses the following National ScienceEducation Standards (NRC 1996)

Content StandardsGrades K–4Grades K–4Grades K–4Grades K–4Grades K–4Standard B: Physical ScienceStandard B: Physical ScienceStandard B: Physical ScienceStandard B: Physical ScienceStandard B: Physical ScienceLight, Heat, Electricity, and Magnetism (K–––––4)

• Light travels in a straight line until it strikesan object. Light can be reflected by a mir-ror, refracted by a lens, or absorbed by theobject.

Grades 5–8Grades 5–8Grades 5–8Grades 5–8Grades 5–8Standard B: Physical ScienceStandard B: Physical ScienceStandard B: Physical ScienceStandard B: Physical ScienceStandard B: Physical ScienceTransfer of Energy

• Light interacts with matter by transmission(including refraction), absorption, or scat-tering (including reflection). To see an ob-ject, light from that object—emitted by orscattered from it—must enter the eye.

Teaching StandardsStandard A:Standard A:Standard A:Standard A:Standard A:Teachers of science plan an inquiry-based scienceprogram for students.Standard B:Standard B:Standard B:Standard B:Standard B:Teachers of science guide and facilitate learning

the water?” Everyone agreed the pencil in the glass ofwater looked like two pencils under the water. Why didthey think it looked like this? One student suggested, “Itmight be something about the surface of the waterbecause when you look on the side it looks different.”

We explained something happened when lighttraveled into and out of water that was different fromlight traveling in air, and it made the pencil look bentor crooked. The light slowed down in the water,causing the path of the light to shift slightly as ittraveled through the water. All the light waves re-flecting off the part of the pencil under the water hitour eyes at a different place than they would if thepencil were not in the water.

We said that light is refracted when it shifts or movesin its path from the object to our eyes, leading us to seethe object as bent or crooked—or making it appear liketwo pencils under the water.

Visible light has all the colors of the rainbow in it.Refraction also was evident in our last activity, “Mak-ing a Rainbow.” Sometimes refracted light wavesspread out so we can see the different colors thatmake up visible light. White light is a combination ofthe colors that we see when we see a rainbow. Whenwhite light is absorbed incompletely (part of it isreflected to our eyes) then we see the color that is thepart of white light that was not absorbed. That is whywe see colors. Shining a strong light (like an overheadprojector light) through a prism can spread out thewaves so we see the different colors.

Some students wondered if the colors in the rainbowwere always in the same order, like the colors in theprism. We wrote ROYGBIV on the board and toldthem those letters stood for the colors in the rainbow—red, orange, yellow, blue, green, indigo, and violet, alsocalled the visible spectrum. We explained that there arealso other “colors” in the rainbow that our eyes cannotrespond to, such as infrared and ultraviolet.

Turning on the LightProviding hands-on science experiences for elementarychildren can be a challenge because of the difficulties ofallotting the time and finding the necessary materials. Ascience circus format makes the task of designing goodscience lessons easier because less time and fewer ma-terials are needed than when doing activities sequen-tially or individually.

Perhaps the greatest benefit to teachers of using thescience circus format is not the ease of use but theoutcomes produced when students generate their ownunderstandings through interaction with real phenom-ena. In one day of science activities these elementarystudents observed phenomena, compared ideas with

others, and tested new ideas against their old ideas tosee if they needed to change their old ideas. The stu-dents had joined Isaac Newton in the quest for under-standing the mysterious substance known as light. n

Juanita Jo Matkins (jmatkins@gmu.edu) is an assis-

tant professor in the Graduate School of Education at

George Mason University in Fairfax, Virginia and

Assistant Director of the Center for Restructuring

Education in Science and Technology. Jacqueline

McDonnough (jtmcdonnough@vcu.edu) is an assis-

tant professor of science education at Virginia Com-

monwealth University in Richmond, Virginia.

ResourcesNational Research Council (NRC). 1996. National Science

Education Standards. Washington, D.C.: National Acad-emy Press.

Koch, J. 1996. Science Stories: Teachers and Children asScience Learners. Boston: Houghton-Mifflin.

InternetProperties of Lightsol.sci.uop.edu/~jfalward/physics17/chapter12/chapter

12.html