Physics Education Research

Physics Education Research:the key to improving student learning: 

Physics Education Research: the key to improving student learning Lillian C. McDermott Department of Physics University of Washington Seattle, Washington

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Physics Education Group Physics Ph.D. Graduates 22 (1979-2008) Physics Ph.D. Students Isaac Leinweber Tim Major Benjamin Pratt Amy Robertson Brian Stephanik Faculty Lillian C. McDermott Paula Heron Peter Shaffer MacKenzie Stetzer Lecturer Donna Messina (K-12 teacher) Research & Teacher Education Coordinators Our coordinated program of research, curriculum development, and instruction is supported in part by grants from the U.S. National Science Foundation. Karen Wosilait and Nina Tosti 2 Post-doctoral Research Associates 12 (1985-2008)

Discipline-based research on learning and teaching: 

Discipline-based research on learning and teaching differs from traditional education research (in which emphasis is on educational theory and methodology) focuses on student understanding of science content is an important field for scholarly inquiry by science faculty (need deep understanding of content and access to students) Discipline-based education research can be a useful guide for improving student learning from the elementary to the graduate level.

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conduct systematic investigations apply results (e.g., develop instructional strategies) assess effectiveness of curriculum document methods and results so that they can be replicated report results at meetings and in papers These are characteristics of an empirical applied science. Perspective: Teaching is a science (as well as an art). Procedures: Physics Education Group 4

Physics Education Group: 

Physics Education Group 5

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Student populations (at UW and at pilot sites) Introductory students (physics, engineering, other sciences) Underprepared students K-12 teachers (preservice and inservice) Engineering students beyond introductory level Advanced undergraduates and graduate students Context for research and curriculum development 6

Focus of researchis not on teaching by instructorsbut is on learning by students: 

Focus of research is not on teaching by instructors but is on learning by students identifying what students can and cannot do designing instruction to develop functional understanding* assessing effect on student learning * ability to do the reasoning necessary to construct and apply conceptual models to the interpretation of physical phenomena

Evidence from research indicates a gap: 

Evidence from research indicates a gap Instructor Student Course goals Gap is greater than most instructors realize. 8

Traditional approach: 

Traditional approach instructor’s present understanding of subject instructor’s belief that he or she can transmit “knowledge” to students instructor’s personal perception of student ignores differences between physicist and student: small for future physicists (<5% of introductory course) large for most students is based on: 9

Systematic investigations of student learning(at the beginning, during, and after instruction): 

Systematic investigations of student learning (at the beginning, during, and after instruction) individual demonstration interviews for probing student understanding in depth written questions (pretests and post-tests) for ascertaining prevalence of specific difficulties for assessing effectiveness of instruction descriptive studies during instruction for providing insights to guide curriculum development What are students thinking?

Students with similar background tend to: – have similar ideas at same stage of instruction  – respond in similar ways to same instructional strategy : 

Students with similar background tend to: – have similar ideas at same stage of instruction – respond in similar ways to same instructional strategy Need for control groups is minimized when: – student populations are large – goal of an instructional strategy is a large change

“An investigation of student understanding of the real image formed by a converging lens or concave mirror,” F. M. Goldberg and L.C. McDermott, Am. J. Phys. 55 (1987).  “Development and assessment of a research-based tutorial on light and shadow,” K. Wosilait, P.R.L. Heron, P.S. Shaffer, and L.C. McDermott, Am. J. Phys. 66 (1998).“Bridging the gap between teaching and learning in geometrical optics: The role of research,” P.R.L. Heron and L.C. McDermott, Opt. & Phot. News 9 (1998).: 

“An investigation of student understanding of the real image formed by a converging lens or concave mirror,” F. M. Goldberg and L.C. McDermott, Am. J. Phys. 55 (1987). “Development and assessment of a research-based tutorial on light and shadow,” K. Wosilait, P.R.L. Heron, P.S. Shaffer, and L.C. McDermott, Am. J. Phys. 66 (1998). “Bridging the gap between teaching and learning in geometrical optics: The role of research,” P.R.L. Heron and L.C. McDermott, Opt. & Phot. News 9 (1998). Identifying and addressing student difficulties with conceptual models for light “An investigation of student understanding of single-slit diffraction and double-slit interference,” B.S. Ambrose, P.S. Shaffer, R.N. Steinberg, and L.C. McDermott, Am. J. Phys. 67 (2), 1999. “Addressing student difficulties in applying a wave model to the interference and diffraction of light,” K. Wosilait, P.R.L. Heron, P.S. Shaffer, and L.C. McDermott, Physics Education Research: A Supplement to the American Journal of Physics 67 (7), 1999. Physical Optics Geometrical Optics

Interpreting and applying a wave model for light : 

Interpreting and applying a wave model for light Examples of conceptual difficulties from written examinations and individual demonstration interviews Physical Optics

Determining what students can and cannot do: 

Determining what students can and cannot do

Questions on single-slit diffractionGiven after standard instruction in introductory calculus-based course: 

Questions on single-slit diffraction Given after standard instruction in introductory calculus-based course Would minima appear on a distant screen? If so, find the angle to the first minimum. Light of wavelength l is incident on a slit of width a = 4l. Quantitative question (N ~130)

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What students can and cannot do Comparison of performance on quantitative and qualitative questions.

(30 modern physics students, 16 introductory students): 

(30 modern physics students, 16 introductory students) Interview task: single-slit diffraction Situation: Distant light source, mask with slit, and screen Task: What would be observed on the screen as slit is narrowed? Explain. Many serious difficulties emerged during the interviews.

Diagrams drawn by student: 

student explanation: light must “fit” through slit mistaken belief: the amplitude of a light wave has a spatial extent Diagrams drawn by student

Written exam question: double-slit interference : 

Sketch what would appear on the screen when the left slit is covered. Explain. The pattern shown appears on a screen when light from a laser passes through two very narrow slits. Written exam question: double-slit interference 19

Responses reminiscent of geometrical optics: 

Responses reminiscent of geometrical optics tendency to associate each bright region with a particular slit (use of a hybrid model: geometrical and physical optics) pattern stays the same or gets dimmer pattern with both slits uncovered When one slit is covered: 20

Illustration of research and curriculum development: geometrical optics(simpler context than physical optics): 

Illustration of research and curriculum development: geometrical optics (simpler context than physical optics) 21

What students could do(after standard instruction):: 

22 What students could do (after standard instruction): Solve problems algebraically and with ray diagrams Example: An arrow, 2 cm long, is 25 cm in front of a lens whose focal length is 17.3 cm. Predict where the image would be located.

What students could not do:: 

23 Predict effect on screen (1) if the lens is removed (2) if the top half of the lens is covered (3) if the screen is moved toward the lens Individual Demonstration Interviews: both before and after instruction What students could not do: Correct 50% 35% 40%

Generalizations on learning and teaching inferred and validated from research have helped guide thedevelopment of curriculum.: 

Generalizations on learning and teaching inferred and validated from research have helped guide the development of curriculum. 24

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? Facility in solving standard quantitative problems is not an adequate criterion for functional understanding. Questions that require qualitative reasoning and verbal explanations are essential for assessing student learning and are an effective strategy for helping students learn. 25

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? Connections among concepts, formal representations (diagrammatic, graphical, etc.) and the real world are often lacking after traditional instruction. Students need repeated practice in interpreting physics formalism and relating it to the real world. 26

Question for research: What happens if there is no lens? : 

27 Question for research: What happens if there is no lens? Research led to identification of a more basic difficulty. Principal rays locate image but are not necessary to form it. Area of lens affects only brightness, not extent, of image. For every point on an object, there is a corresponding point on the image. Students could all state that light travels in a straight line but did not recognize that:

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What students could not do: (either before or after standard instruction in introductory university calculus-based physics) Sketch what you would see on the screen. Explain your reasoning.

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Single bulb Two bulbs Long-filament bulb Correct responses Pretest (N >> 1000 students) Sketch what you would see on the screen. Explain. 29

Fundamental difficulty:Lack of a functional understanding of a basic ray model for light : 

Fundamental difficulty: Lack of a functional understanding of a basic ray model for light Light travels in a straight line. Every point on an object acts like a source of an infinite number of rays emitted in all directions. 30

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31 ? A coherent conceptual framework is not typically an outcome of traditional instruction. Students need to go through the process of constructing models and applying them to predict and explain real-world phenomena.

On certain types of qualitative questions, student performance is essentially the same:: 

On certain types of qualitative questions, student performance is essentially the same: before and after instruction in calculus-based, algebra-based, and “conceptual” courses whether topics seem ‘complex’ or ‘simple’ with and without demonstrations with and without standard laboratory in large and small classes regardless of popularity of the instructor 32

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? Teaching by telling is an ineffective mode of instruction for most students. Students must be intellectually active to develop a functional understanding. 33

Need for a different instructional approach(“guided inquiry”): 

Need for a different instructional approach (“guided inquiry”) Physics by Inquiry Laboratory-based, self-contained curriculum designed primarily for K-12 teachers, but suitable for other students Tutorials in Introductory Physics Supplementary curriculum designed for use in standard introductory physics courses 34

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Curriculum Development Research Instruction Iterative cycle for development of curriculum 35

Emphasis in PbI and in Tutorials is on:: 

Emphasis in PbI and in Tutorials is on: constructing concepts and models developing reasoning ability addressing known difficulties relating physics formalism to real world not on solving standard quantitative problems 36

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Students are guided in constructing a basic ray model from their direct experience with light sources and apertures of different shapes. Questions that require qualitative reasoning and verbal explanations help students develop a functional understanding through their own intellectual effort. Curriculum explicitly addresses conceptual and reasoning difficulties identified through research. This type of laboratory-based instruction is especially important for pre-university teachers. Physics by Inquiry Instruction on Geometrical Optics

Inspiration for development of Tutorials in Introductory Physics: 

Inspiration for development of Tutorials in Introductory Physics We found that elementary school teachers who had learned from Physics by Inquiry could do better on certain types of questions than engineering and physics majors.

Results with Physics by Inquiry module.: 

Results with Physics by Inquiry module.

Application in 9th-grade: 

Application in 9th-grade Success rate of 9th-grade students with: under-prepared inservice teacher < 20% well-prepared (PbI) preservice teacher ~ 45% well-prepared (PbI) inservice teacher ~ 85% With under-prepared inservice teacher ~ introductory university students With well-prepared (PbI) inservice teacher > graduate students (~65%)

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41 to improve student learning in introductory course (constraints: large class size, breadth of coverage, and fast pace) Need to secure mental engagement of students at deep level Requirement to develop a practical, flexible, sustainable approach Challenge

Response: 

42 Response to improve instruction in introductory physics through cumulative, incremental change (evolution not revolution) by recognizing the constraints imposed by lecture-based courses by developing research-based tutorials that supplement standard instruction with a modified version of the intellectual experience provided by Physics by Inquiry

Tutorials respond to the research question:: 

Tutorials respond to the research question: Is standard presentation of a basic topic in textbook or lecture adequate to develop a functional understanding? (i.e. the ability to do the reasoning necessary to apply relevant concepts and principles in situations not explicitly studied) If not, what needs to be done?

Tutorial sequence consists of: : 

44 Tutorial sequence consists of: Pretest (paper or web-based) Worksheet (collaborative small groups) Homework (individual) Post-test (course examinations)

Note that research-based is not the same as research-validated.: 

Note that research-based is not the same as research-validated. Pretests are not enough. Post-tests are necessary.

Carefully sequenced questions guide students in investigating geometric images produced by various combinations of apertures and light sources.: 

Carefully sequenced questions guide students in investigating geometric images produced by various combinations of apertures and light sources. Tutorial: Light and Shadow

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administered after tutorial Light and shadow Post-test 1 Sketch what you would see on the screen when the bulbs are turned on.

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Revision to tutorial (and to Physics by Inquiry) Students consider a true extended source (frosted light bulb).

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administered after revised tutorial Post-test 2 Sketch what you would see on the screen when the bulbs are turned on.

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Note: Results not as good as with Physics by Inquiry (75% vs 90%) but less time spent.

Practical criterion for effectiveness of a tutorial:: 

Practical criterion for effectiveness of a tutorial: Post-test performance of introductory students matches (or surpasses) pretest performance of graduate students. (75% vs. 65%)

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? Certain conceptual difficulties are not overcome by traditional instruction. (Advanced study may not increase student understanding of basic concepts.) Persistent conceptual difficulties must be explicitly addressed. 54

Can explanations by lecturer substitute fordirect experience of students?? : 

Can explanations by lecturer substitute for direct experience of students?? Two professors at UW tried to save time through demonstrations and homework Results were much poorer, even for honors students . (< 45% correct vs 75%)

Example of assessment of student learning through pretesting and post-testing in physical optics: 

Example of assessment of student learning through pretesting and post-testing in physical optics

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Example of pretest on multiple-slit interference The pattern at right appears on a distant screen when coherent red light passes through two very narrow slits separated by a distance d. Suppose that a third slit is added as shown: Would the intensity at point B increase, decrease, or remain the same?

Tutorials guide students in constructing and applying a basic wave model for light.: 

Develop basic interference concepts in context of water waves path length (and phase) difference superposition mathematical formalism Make appropriate analogies between water and light waves Extend model for two-slit interference to more than two slits to single-slit diffraction to combined interference and diffraction Resolve specific difficulties through their own intellectual effort Extend and apply model in different situations Tutorials guide students in constructing and applying a basic wave model for light. Worksheets and homework help students:

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Example of post-test on multiple-slit interference Would the intensity at point B increase, decrease, or remain the same? The pattern at right appears on a distant screen when coherent red light passes through two very narrow slits separated by a distance d. Suppose that a third slit is added as shown:

Results from pretest and post-test on multiple-slit interference: 

Results from pretest and post-test on multiple-slit interference Does the intensity at point B (a maximum) increase, decrease, or remain the same? Pretest Post-test

Assessment of student learning: 

On qualitative problems: much better On quantitative problems: typically somewhat better sometimes much better Effect of tutorials on student performance Assessment of student learning despite less time devoted to solving standard problems (Emphasis is on reasoning.) On retention: sometimes much better 61

? Growth in reasoning ability does not result from traditional instruction.: 

? Growth in reasoning ability does not result from traditional instruction. Scientific reasoning skills must be expressly cultivated. Concepts and reasoning are inseparably linked and must be taught together.

Reflection on some important features of : 

Reflection on some important features of Curriculum is self-contained and laboratory-based (simple equipment). Students do the reasoning needed for the development and application of concepts and construction of models. Conceptual and reasoning difficulties that have been identified by research are explicitly addressed. Students work in small groups (collaborative learning and peer instruction). Instructors teach by questioning, not by lecturing. Emphasis on explanations of reasoning

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Results from research indicate: many students encounter same conceptual and reasoning difficulties same instructional strategies are effective for many students are: generalizable beyond a particular course, instructor, or institution reproducible become: publicly shared knowledge that provides a basis for acquisition of new knowledge and for cumulative improvement of instruction 64

Discipline-based education research can be an effective guide for improving the learning of science from elementary school to the graduate level. Such research at the university level is best conducted in science departments because it requires:: 

Discipline-based education research can be an effective guide for improving the learning of science from elementary school to the graduate level. Such research at the university level is best conducted in science departments because it requires: Deep understanding of the subject. Ready access to students while they are learning. These conditions are not usually found outside of science departments.