Presentation is loading. Please wait.

Presentation is loading. Please wait.

From a subtractive to multiplicative approach Two concept-driven interactive pathways on the selective absorption of light Laurence Viennot PRES Sorbonne.

Similar presentations

Presentation on theme: "From a subtractive to multiplicative approach Two concept-driven interactive pathways on the selective absorption of light Laurence Viennot PRES Sorbonne."— Presentation transcript:

1 From a subtractive to multiplicative approach Two concept-driven interactive pathways on the selective absorption of light Laurence Viennot PRES Sorbonne Paris Cité, University Paris-Diderot LDAR

2 Multiple objectives … Engage students with physics Simplify Help students construct a first idea of NOS: inquiry, reasoning Consistency as a goal (NOS), as a need (reasoning) Highlight links between phenomena, between theories and phenomena Develop critical stance in students

3 Oversimplification: Some intrinsic risks -Wish to show + belief that seeing is understanding -« Echo-explanation » : mirroring students’ common ways of reasoning - Ignoring some variables, phenomena : conceptual reduction - Uncontrolled generalisation - « All-or-nothing » approach - … As a result: serious inconsistencies Web site EPS-MUSE; Viennot 2014

4 Can we help students develop their critical faculty without a conceptual basis? Without an access to a conceptual structure, can students understand that science aims at a unified (as much as possible) description of the material word? - There is a real danger that Inquiry-based learning presents scientific knowledge as “knowledge in pieces”. Ogborn 2012 - These students...(France, end upper second. 2013) see physics as disordered and anarchical. Zabulon 2013

5 Co-development of critical attitude and conceptual understanding Critical attitude Comprehension Threshold of comprehension

6 Co-development of conceptual understanding (including a math component) and critical stance The value of « concept-driven interactive pathways » In teaching practice Stressing coherence and links

7 Concept-driven interactive pathway Centered on conceptual development and critical attitude, coherence Interactive: intellectual interaction with teacher and/or other students Progressive: each step may serve to construct the next step 7

8 8 Viennot de Hosson 2012a,b Workshop WCPE 2012: Muse project CDIP 1 Concept-driven interactive pathway Absorption by pigments beyond a dichotomic approach Research investigation, 8 interviewees*, 3rd year University A workshop, WCPE meeting in Istanbul 2012, N=22, MUSE project *Teaching interviews, Komorek & Duit 04

9 9 A pigment absorbs Pigments -absorb a part of the light received -diffuse the rest Reminder absorbs White light

10 Phase « P/A »: Presence / Absence of light: 10 Blocking off the light Chauvet 1996

11 An experiment and a question 11 A dim ambiant light A laser beam (632 nm) is directed toward black or various coloured areas Will the impact on Black, Green, Blue, … be visible? If yes, which colour?

12 CDIP 1 12 All or nothing? More or less

13 PhasegoalMaterial setting Aspects of the discussion P/AStudents are reminded of the classical rules First observation of their reactions Predictions with arguments, observation, discussion, recapitulation. Table of rules explained and left to students M/L1Intense coloured light on pigments: Do students transfer or not of classical rules if yes how? A laser pointer + (same as M/L/1) + reflectivity curves of pigments Predictions with arguments: Impact visible or not, if yes, description of the impact, with arguments M/L2 M/L3 Performing the experiment: how do they react ? …do they -use M/L approach? -understand multiplicative aspect of absorption ? -explain the difference between experiments used in phases P/A and phase M/L Strong destabilisation expected. Important input on behalf of the interviewer to help students comprehend the meaning of the curves M/L4Global evaluation of the designExpressing feelings 13 The interviews: global structure

14 Main results ML1 predictions With black, blue, green, and cyan (“absorbing red light”), students (6/8) predicted that the impact of the laser beam would not be visible on the background for at least three of these four areas. (as with classical rules ) 14 Some doubts: - In principle, I can’t see anything. But does that black absorb really everything? I don’t know! -Can we see…? can we guess the red colour on a black background …? …but I don’t know! -I am aware that when the laser beam will be sent on the sheet (with blue pigment), we will see something, because I have already played with a laser. The first allusions to the brightness of what is seen happened in the case when a red paper is illuminated by the (red) laser beam.

15 Main results ML2 after the experiment Surprise, frustration: all - Normally, it should be absorbed. - (my predictions) Err…, they are wrong(…), it’s pretty hard to understand - I’m lost, it’s frustrating. Impacts +/- bright, two groups of pigments: all +/- light, absorption: 6/8. - When I say there will be no impact, err.. There is less light. - Perhaps, it (red light) was not completely absorbed. 15

16 Graphs: a lapse of time to understand their meaning - Difficulties: quasi all Err …actually, it’s not very intuitive with percents! - Only 4/8 make explicit the multiplicative aspects 10% of very intense, it makes something! … When it’s more luminous, the 10% are more consequential - The tails of the curves: 2/8 only understand their effect Acknowledging the importance of the power of the sources: all but without necessarily showing a sound understanding 16 Main results ML3 with reflectivity curves

17 Surprise (again)6/8 -Sure, I will not forget -Before, I never thought of that Satisfaction /interest8/8 -(With the graphics), I understand - Before, I never thought of that -but …- I will have to think further 2/8 - I am pleased with the interview but not with my answers Meta cognitive and critical comments5/8 - They just absorb less. (…), we were thinking all or nothing. (…). It was total. - We have to be careful (with rules) -The (classical) rules have a certain validity -There is something in common (with classical rules) -… It means that physics has a relative value 17 Main results ML4 Expressing feelings

18 Main results: recapitulation Strong destabilisisation The two groups of pigments are unanimously identified: « More or less » unanimously expressed All interviewees realise that strong sources may « invalidate » the « all or nothing » rules. Meta cognitive and critical comments But difficult access to the meaning of percentages CDIP 1 Consequently …

19 19 Viennot de Hosson 2013-2014 Workshops: Muse project 2013 CDIP 2 Concept-driven interactive pathway about Transmission of light through transparent media V/s thickness Research investigation, 6 interviewees*, 4th year Univ. A workshop in EPEC/ICPE 2013 (Prague, N=16), ESERA 2013 (Nicosie, N=12) MUSE project *Teaching interviews, Komorek & Duit 04

20 Transmission of light through transparent media V/s thickness CDIP 2 20 Viennot de Hosson Workshops: Muse project 2013 For each wave length, each successive « layer » (of same given « small » thickness) multiplies the incident light by the same factor (<1): a percentage. This may change the shape of the transmission curve with thickness, therefore also the colour of the transmitted light. Introduction to exponential dependance

21 Which operation do you associate to the action of filters: + - * / ? Explain your reasoning A question absorbs Unanimous response: subtraction A reminder Mi Er rather…absorbed, there is really something taken off. Int Taken off. That’s what makes you say « subtraction » Mi That’s it.

22 Question Draw the curves accounting for the transmission of light through two, then three layers, knowing the curve for one layer:

23 a One layer b Two layersc Three layers Basis for a correct answer: For each wavelength, each successive « layer » multiplies the incident light by the same percentage 0,95*0,95 0,95*0,95*0,95 0,3*0,3 0,3*0,3*0,3

24 Absorption curves: students’ drawings

25 The observed spectra And with magenta …

26 Int : What did you use when constructing your answer, a line of reasoning founded on which type of operation? Vi: Subtraction, mainly. To : We add subtractions. Ch : It’s still a subtraction, a wavelength is taken off. Int : Even getting the peak thinner is a subtraction ? To : Yes it’s, yes, still subtraction. Blue is taken off. Students’ reactions to the experiment: do they change their curves? From a focus on subtraction…

27 Mi : Given that it is proportional, … (adding filters) we will end by selecting the spectral band of greatest transmission factor.. Th : We’ve just seen that differences were majored when layers were added. Mi : Yes, finally, yes, once we speak of proportions, of the fact that a filter let pass eighty per cent, hence two filters let pass eighty per cent of eighty per cent. Yes, that’s really clear. More, we can now understand the fact of increasing the number of layers. (Int: mathematical operation?) Multiplication. Reactions to the xperiment performed (continued) … to a comprehension of the role of multiplication … and some meta cognitive comments To : Even after having done this (a multiplication) right from the beginning, I wouldn’t have interpreted this as a multiplication.

28 One layer: at zenith Transmission of light through layers of air

29 The atmosphere as a filter? A non obvious view! Ya : I see what hasn’t been diffusively reflected. It’s a dispersive medium, it’s not a filter. Int : When you’re told that the sky is blue, the blue light is diffusively reflected, it makes you think of which mathematical operation, with respect to the incoming light? To : Subtraction. What is transmitted is the rest. Ya : Even before doing it (the operation), I knew it was multiplicative. By contrast, from this to see the atmosphere as a filter, this, before, I wouldn’t have done it. Ya : The atmosphere as a filter, I had no idea of seeing things like that. … and still some meta-cognitive comments

30 Given the transmission curve for one layer …





35 Understanding why we see the sun red at sunset

36 Transmission of light through layers of pumpkin seeds oil

37 More and more pumpkin seeds oil

38 Transmission spectrum? Kreft, S. & Kreft, M. 2007. Physicochemical and physiological basis of dichromatic colour. Naturwissenschaften 94, 935-939. A bold simplification






44 PhasegoalMaterial setting Aspects of the discussion RemStudents are reminded of the classical rules +cones Question: which operation comes to your mind:+,-,*,/? A colour mixer The students appropriate the classical rules, answer question “which operation …?” Filt-expDraw the curves accounting for the transmission of light through two, then three layers Spectra observed Predictions with arguments Filt-obs Atm Performing the experiment: Do they change their curves? – See the situation as a filtering case. Transform the curve Students asked to reconsider the curves The interviewer provides help for calculation and explains how to use the sensitivity curves (cones).. OilObserve oil’s colours, then apply a multiplicative procedure to the curve idem GeneAsk for an appropriate functionHelp find exponential FeelGlobal evaluation of the designExpressing feelings 44 The interviews

45 Students’ reactions to this CDIP

46 Satisfaction /interest/newness To Exponential function as we just saw it, it’ natural, definitely. Th I will not put any mark, but it would be very good, and I am intellectually very satisfied, and I end this interview with something righter, it means that it’s been useful. Th I wouldn’t have spontaneously used the word multiplication, I was not reasoning like that before coming here. (…) 46 Expressing feelings 3rd year university

47 Meta cognitive comments Th Perhaps, I would use the operation with the right data, but if I was asked an explanation, I would never have used the word multiplication. Critical stance To … Given this, should we tell our students, should we use the law of additivity bla bla bla! Is it correct to use it? No, it’s true, additivity is OK, it’s for subtractivity, (that there is a problem). Vi Show subtraction, if I can say, of colours, and come back afterwards on something that comes down to percentages, it’s rather, err, I don’t know if you would’ve presented it like that. (…) For a student who is not used to it, it might be very disturbing. - I- I 47 Expressing feelings: 4th year university

48 Satisfaction /interest/newness - Tough ideas worked through in groups. Useful discussions -Step by step, new ideas -A simple topic with profound knowledge -Guided process in a sequence with a big framework on the ground -Made me think -Approach to exponential, very interesting with context -Good assignment that really make you think -…. activities that extended my thinking - …elements of self doubting and surprise 48 Expressing feelings: workshop participants EPEC-ICPE and ESERA (2013) EPEC-ICPE N= 16 (out of 22 participants) Interesting: 16/16 (max rating: 3) useful 12/16 (max rating: 3) ; 4/16 (rating: 2) ESERA N= 16 (out of 16 participants) Interesting: 16/16 (max rating: 3) useful 11/16 (max rating: 3) ; 4/16 (rating: 2); 1 (rating: 1)

49 Meta cognitive comments -It made me think about things I knew about perhaps intuitively, but I still think it was as if I did not know about them previously. Critical stance - The use of different thickness, we usually do with only one and I had the idea of subtraction 49 Expressing feelings: workshop participants EPEC-ICPE, ESERA (2013)

50 The reasons of a CDIP Searching for fundamental ideas (« x » instead of « -», ultimately, « x » means probabilist) While trying to keep formalism reduced Searching/taking into account students’ ideas (subtraction) Taking into account teaching rituals (« subtractive » synthesis, absorption « all or nothing, » ) Stressing links (atmosphere as a filter) Keeping simplification under control (non-toxical modelling) “Conciliation of a rather classical teaching scenario – one that is interactive, progressive, respecting a constraint of formal simplicity – with profound and fruitful ideas.” A new spotlighting for “well known” ideas

51 – Extreme conceptual reduction: There is a price to pay, need to be very careful, avoid ruining consistency, keep simplification under control, mind rituals – Students’ reactions: They appreciate consistency, need to reach a threshold of comprehension before daring to express their frustration in this respect, need: co-development of critical thinking and conceptual comprehension subtractive? – Showing that science aims at a unified « description » of the world: value of stressing conceptual coherence and links. -The merits of stressing « new » spotlightings of the content: « New » does not mean reinventing physics. Means attention to aspects of physics commonly disregarded, or kept implicit. Multiplicative instead of subtractive Concluding remarks

52 – Nourish a more balanced discussion about the objectives (content/ competences) and modalities of physics teaching. – In particular, see « active learning » as compatible with several types of learning activities, including critical dialogue. You made me think – Need to propose various approaches and means to be used in class practice, thus enlarging the range of teachers’ choices. Ex: CDIPs on the MUSE website MUSE More Understanding with Simple Experiments Education, MUSE Concluding remarks …

53 Perspectives for research – More fine-grained investigations on what triggers a critical stance and a renewed exigency in students. – Investigate meta cognitive-affective components of students’ intellectual paths: *Awareness of the distance between doing and understanding: « Perhaps, I would use the operation with the right data, but if I was asked an explanation, I would never have used the word multiplication. … » * Intellectual satisfaction as an outcome of teaching/learning process

54 Thank you for your attention


56 56 Thus in the UK, the issue became how to develop science courses genuinely designed for the whole school population. This became something of a national obsession, not shared by other countries. One slogan devised for this was “Relevance”. Complex issues need complex solutions, but they generally get simple slogans to encapsulate and make memorable these solutions: “Relevance”, “Ask Nature”,“Science for All”, “Hands On”, “Science Workshop”, “Learning by Doing”. MaoZedong had a genius for inventing them, in a very different context. Be wary of these slogans. They are needed, even essential, to help people remember the point and perhaps to focus energy and enthusiasm. But they rarely speak plainly. I remember being asked near the start of my second development project Advancing Physics, what its slogan would be. I was at first embarrassed to find that I had no good answer. Maybe “Variety”, I said – if you want to appeal to more people you have to offer more ways of being attractive. The answer suggests its own limits. It cannot be right to focus a whole course on being attractive, at any cost. So there must be a basic truthfulness to the nature of the subject – in this case physics. But now this is not a slogan, but the statement of a complex problem. I cannot say that I am sorry, even if it makes it hard to tell people what is the ‘essential new idea’ behind Advancing Physics. In fact, I am suspicious of any educational development that passionately believes in its own slogans. I do not much believe in one-shot solutions – ‘magic bullets’. I conclude that a theory that provides guidance on producing teaching materials will suffer the same difficulty: that simple slogans encapsulating its ideas are needed, but are also dangerous. Ogborn, J. 2010. Curriculum development as practical activity In K. Kortland (ed.): Designing Theory- Based Teaching-Learning Sequences for Science Education. Utrecht: Cdβ press,69-90. Un grand acteur de développements curriculaires (UK)

57 Critical attitude, conceptual development, conceptual links Perhaps the most difficult, and yet the most important kind of event to create in the classroom is critical dialogue, which recognises that inquiry proceeds by being critical of proposed ideas. It cannot help that essentially no examination questions ever require the student to offer a criticism, even the simplest. Such a focus on being critical is surely one of the greatest deficiencies that the movement for inquiry based learning needs urgently to face. There is a real danger that Inquiry-based learning presents scientific knowledge as “knowledge in pieces”. Ogborn 2012

58 Links needed between math and physics Still worth, most of the students think that there is no link between mathematics and physics, a domain in which all the results are easily obtained (…)“with the hands”. (…) These students don’t have even the bases that their predecessors previously acquired, and they see physics as disordered and anarchical. On the linking between secondary teaching and higher education in physics and chemistry Zabulon, T., Dec. 2013 61e National Conf. of Union of Physics and Chemistry Teachers BUP, pp-2011-2016 In our search for a possible explanation for the strikingly parallel decline in physics achievements for the «specialist» at upper secondary school, we have established a set of possible factors. (…) the interdependence between mathematics and physics is weakened in the present curriculum in Sweden compared to 1995 ( …) many students do not see the connection between the mathematics in the math class and the mathematics they actually use in physics (e.g.Taber, 2006). Interpreting the Norwegian and Swedish trend data for physics in the TIMSS Advanced Study S.LIE, C. ANGELL & A. ROHATGI 2012 Nordic Studies in Education, Vol. 32, pp. 177–195 Oslo

59 Viennot L. 2006.Teaching rituals and students' intellectual satisfaction, Phys. Educ. 41, 400- 408. Mathé, S., & Viennot, L. 2009. Stressing the coherence of physics: Students journalists' and science mediators' reactions, Problems of education in the 21st century. 11 (11), 104- 128. Viennot, L. 2009. Physics by inquiry: beyond rituals and echo-explanations, In New Trends in Science and Technology Education, G. Santoro (Ed.): “New Trends in Science and Technology Education” Conference, Modena, CLUEB, Bologna Viennot, L. 2010. Physics education research and inquiry-based teaching : a question of didactical consistency, In K. Kortland (ed.): Designing Theory-Based Teaching-Learning Sequences for Science Education. Utrecht: Cdβ press, 37-54. Viennot, L. & de Hosson 2012 Beyond a dichotomic approach, the case of colour phenomena. International Journal of Science Education, 34:9, 1315-1336. Viennot, L. & Décamp, N. Analysing texts about radiocarbon dating: co-development of conceptual understanding and critical attitude, ESERA 2013 More Understanding with Simple Experiments: education, MUSE Viennot, L. 2014. Thinking in Physics, The pleasure of reasoning and understanding in physics. Springer/Grenoble Science Komorek M, Duit R. (2004): The teaching experiment as a powerful method to develop and evaluate teaching and learning sequences in the domain of non‐linear systems. IJSE, 26(5):619–633. pOpO pOpO pOpO pOpO

60 Ogborn, J. 2012. WCPE Istanbul, keynote address, Curriculum Development in Physics: Not quite so fast! Zabulon, T. 2013 On the linking between secondary teaching and higher education in physics and chemistry 61e National Conference of Union of Physics and Chemistry Teachers (UdPPC) Reports on round tables BUP, Dec. 2013, pp-2011-2016 Lie, S., Angell, C. & Rohatgi, A. 2012 Interpreting the Norwegian and Swedish trend data for physics in the TIMSS Advanced Study, Nordic Studies in Education, Vol. 32, pp. 177–195 Oslo Editorials, reports Léna, P. 2009b. Europe rethinks education, Science, 326, 23-11-2000 Rocard, Y. 2007, Science Education Now, Report EU22-845, European Commission, Brussels, education_en.pdf education_en.pdf Osborne, J.. Dillon, J. 2008. Science Education in Europe : Critical Reflexions. Nuffield Foundation,,. Allende, J.E. 2008. Academies Active in Education, Science, 321, 29-8-2008. Editorial.“(…) through science education that is based on inquiry, an approach that reproduces in the classroom the learning process of scientists: formulating questions, doing experiments, collecting and comparing data, reaching conclusions, and extrapolating these findings to more general situations

61 A worrying trend that I detect sees new approaches being set up in opposition to each other in an unhealthy dichotomy (…) all too often, approaches to teaching scientific conceptual knowledge are cast as being 'traditional', 'didactic' and 'bad', whilst inquiry approaches are seen as being 'innovative', 'child-centered' and 'good'. My own view in these matters is that there is an appropriate place for all of these forms of teaching: it just depends on what the teacher is trying to achieve. P. Scott Girep 2009

Download ppt "From a subtractive to multiplicative approach Two concept-driven interactive pathways on the selective absorption of light Laurence Viennot PRES Sorbonne."

Similar presentations

Ads by Google