Overview

In this activity, students, working in groups, are asked to answer a series of problems on the wave theory of light and double-slit interference by starting from a drawing instead of a pre-memorised formula. After students have achieved a conceptual understanding of the theory by using drawings, they can start using formulae to solve increasingly harder problems.

Students solve problems 0, 1 and 2 (see attached material for examples) using the drawing of concentric circles.  

Problem2 is quite hard, and most groups are not actually expected to reach a solution; if no ...

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In this activity, students, working in groups, are asked to answer a series of problems on the wave theory of light and double-slit interference by starting from a drawing instead of a pre-memorised formula. After students have achieved a conceptual understanding of the theory by using drawings, they can start using formulae to solve increasingly harder problems.

Students solve problems 0, 1 and 2 (see attached material for examples) using the drawing of concentric circles.  

Problem2 is quite hard, and most groups are not actually expected to reach a solution; if no group reaches a solution in around 25 minutes, the instructor will further explain the problem by presenting the appropriate picture. After the problem and picture are understood, the instructor presents to the students a solution with formulae.

The instructor then describes problem3  which, because of the distances involved, cannot be solved by drawing a picture. If there is still time, students can then begin to work on problem4; if not, they are expected to work on this at home and it will be discussed at the beginning of the following class.

Peer instruction between groups is encouraged - students are told to ask each other for advice and explanations instead of asking the teacher. Of course, the instructor also provides guidance and clarifies concepts.

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Objectives

The purpose of this activity is for students to grasp the concept behind the formulae by first answering a problem using a drawing. This allows them to develop a qualitative, image-based solution in mind instead of simply applying a series of memorised, “correct” formulae.

Context and requirements

Level CEGEP
Discipline Physics
Course NYC Waves, Light, and Modern Physics
Activity Content Wave theory of light; Young’s double-slit interference experiment
Technological Requirements Whiteboards
Best Use Practice

Author’s Notes

Benefits

  • This activity allows students to develop a picture and conceptual understanding of the formulae and the elements that are at play; they can consider the reason for which the formulae exists;
  • This enables students to solve a broader range of conceptually similar problems, instead of simply knowing how to apply a formula to one set of problem statements.

Challenges

  • Approaching a problem this way takes more time than through a traditional teaching mode;
  • There is resistance both on part of students, who may feel the instructor is not really teaching them, and other colleagues unfamiliar with the approach.

Tips

  • This activity is not done at the beginning of the term nor is it the first physics class for the students, therefore most are already familiar with the instructor’s use of this teaching style, which limits resistance.
  • The role of the teacher is to support and accompany the students and mitigate frustration in the concept learning stage, rather than provide correct answers to the problems.

Activity Pedagogical Components

Problem solving

Students solve problems 0, 1 and 2 using the drawing of concentric circles. Students try solving problem 4 at home without the drawings.

Peer instruction

Students ask each other for advice and explanations instead of relying solely on the instructor.

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