Academic journal article Science Scope

Reflecting on Students' Misconceptions about Light: Using Research to Guide Assessment and Instruction

Academic journal article Science Scope

Reflecting on Students' Misconceptions about Light: Using Research to Guide Assessment and Instruction

Article excerpt

From the Sun to oven burners, light is everywhere in our students' lives. Yet despite its ubiquity and necessity, light is intangible, and students find the phenomenon abstract and confusing. Many students have misunderstandings about light as they enter middle school, and it is the responsibility of science teachers to find activities that dispel their mistaken ideas. For example, in an analysis of 227 fifth-grade students' ideas about light and color, Anderson and Smith (1986) discovered that, when asked what happens when someone turns on a light in a dark room, students believed that light filled the room and made it bright. Only 15% of students explained that light continuously comes out of a lamp and hits things. This indicates that students did not think light was in motion. Anderson and Smith also asked students to draw an arrow showing the direction light reflects off of a piece of white wood. Nearly half (48%) did not draw an arrow at all, indicating these students believed the wood absorbed all the light and did not understand that eyes do not see objects, rather eyes detect the light reflected off of objects. This lesson, which can be completed in two 50-minute class periods, begins by eliciting students' preconceptions and then addresses their difficulties in understanding light.

Day 1

Elicit

I begin the lesson by giving each student a copy of the preassessment. The preassessment requires students to answer two questions developed and used by Anderson and Smith (1986) in their two-year study focusing on fifth-graders' misconceptions of light.

1. A girl in a dark room turns on a lamp. What happens then?

A. Light comes out of the lamp until it fills the room; then it stops moving.

B. Light keeps coming out of the lamp and bounces off things.

C. The lamp makes the room bright.

D. I don't know.

2. Draw arrows on the pictures below (Figures 1 and 2) to show what would happen to light from the flashlights after it hits the objects. After drawing the arrows, explain in writing what happens.

This activity is used in a couple of ways. First, it gets students thinking about their ideas. Second, once the preassessment is collected, it is an opportunity for me to see if students' misconceptions are dissimilar to Anderson and Smith's findings. If so, knowing students' alternative ideas helps me modify and guide subsequent instruction. Third, preassessing students' ideas serves as a tool to group students depending on their understanding of the topic. And finally, students' responses to the preassessment are used for a postassessment activity. After instruction, I pass out students' preassessment responses and ask them if they would like to modify, change, or keep the answers they gave before the lesson.

Engage

After the preassessment, I ask my students to gather around the demonstration table, where I have two pieces of cardstock with identically located, dimesized holes. I fold the pieces of cardstock to allow them to stand upright aligned a foot away from each other. Next, I turn off the classroom lights and begin a whole-class discussion by explaining to students that I am going to shine a flashlight toward the holes of the cardstock and asking them to predict what will happen and why. Students think that the light coming out of the first hole will light up all of the second piece of cardstock, and that the light coming out of the second hole will light up much of the wall. This activity demonstrates how light travels in a straight line, not necessarily "filling up a space" as some students might think. Students observe that light coming out of the hole in the first piece of cardstock does not light up the entire second piece of cardstock. Instead, light travels through holes in both the first and second pieces of cardstock and can be seen on the wall. After students have observed the light traveling directly through the two holes without illuminating the second piece of cardstock, I ask them to explain to me what happened and why by posing the question "What does this mean about light? …

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