Light and shadows: a misconception versus a syllabus deadline
A Class 6 science teacher has 34 students and six days before the term examination. A pre-test on light and shadows shows that 70 per cent of the class believe a shadow can form in a completely dark room, and 55 per cent say the shadow is 'on the object' rather than on a surface behind it. The chapter has two more sections to cover. The classroom has windows but no blinds, no adjoining dark room, and only one working torch; the school laboratory is booked by Class 10. The textbook has a single diagram of a shadow. Nine students who attend private tuition answer correctly and are visibly bored. The head teacher has asked all teachers to begin revision by Friday. The teacher has two 40-minute periods available for this topic before revision starts.
1. Should the teacher stop the syllabus and run a predict–observe–explain sequence, or complete the chapter and revise? Justify using how children learn science and the constraints.
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The choice is not between 'syllabus' and 'inquiry' as opposites. The pre-test shows a misconception held by about 24 of 34 students; a textbook diagram is unlikely to shift it because students can read the diagram through their existing idea. Conceptual-change teaching needs the existing idea activated, a discrepant event, a plausible alternative and application. The constraints are six days and two periods, so I would use one 40-minute period for a tightly structured predict–observe–explain sequence and the second for explanation, a short reading and exam-style application. The remaining two sections can be covered in the revision slot with a concept map.
This is not hands-on work for its own sake: the activity is chosen because it directly contradicts two named misconceptions and because the same ideas appear in the examination. I would tell the head teacher that one period is being used for a targeted misconception check and that revision will start on time. I would not spend a week on open inquiry; with 34 students, one torch and no dark room, a demonstration with whole-class prediction is more feasible and more equitable than group practicals.
2. Describe a 12-minute activity using one torch, no dark room and 34 students that directly confronts the 'shadow in the dark' and 'shadow is on the object' ideas.
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Create a 'dark enough' space under a large table or by draping a bedsheet over two desks; total darkness is not needed. A shoebox with a hole is an alternative. Twelve minutes: for 3 minutes, each student writes predictions on a strip for three situations: (a) torch on, pencil between torch and a white chart; (b) torch switched off; (c) torch moved farther away. For 6 minutes, call four students to hold the chart, pencil and torch; switch off the room lights; perform each situation. Ask the class to point to where the dark patch is and place a chalk mark on the chart, not on the pencil. For (b), ask where the shadow went and why. For (c), measure the shadow length with a ruler and record it on the board. For 3 minutes, students correct their prediction strips and write one sentence: 'A shadow is formed on a surface behind an object when light is blocked.' Collect the strips as exit tickets.
Safety: never point the torch at eyes; manage the table corner; use no candle or mains equipment. The key move is making the screen, not the object, the place where the shadow is marked.
3. How will you assess whether the misconception has shifted, given that the exam is in six days?
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Assess the same idea in a new context, not the exact demonstration. Use a three-item probe before and after: a diagram with a torch, ball and screen where students mark the shadow; a true/false-with-reason item about a dark room; and a prediction of what happens when the screen is moved. Mark explanations for the two target ideas: light is blocked, and the shadow falls on a surface behind the object. In the examination, include at least one application item, such as why a shadow is not seen at noon directly under a tree, rather than only a definition.
Sort the 34 exit strips into 'no shift', 'partial' and 'secure' to decide whether one more ten-minute reteach is needed before Friday. Do not treat the nine tuition students' correct answers as evidence of class learning. If more than a third still say a shadow can form in the dark, reteach with a second discrepant event rather than move on. Record the pre- and post-counts in the teacher's diary as evidence of responsiveness, not just as marks.