Reflections on Reflection

Transcription

1 HJS4 HJS5 HJS2 Unformal learning and public understanding GIREP- Seminar 2005 Ljubljana Reflections on Reflection From optical everyday life phenomena to physical awareness The retina is only a window behind which a man is standing Alex Müller The eye is the window of the human body through which it feels its way and enjoys the beauty of the world Leonardo da Vinci H. Joachim Schlichting WWU Münster Germany

2 Slide 1 HJS2 HJS4 HJS5 I am happy for getting the possibility to present the following talk. Half an our is not much time, so I can only sketch the main ideas. And I have to admit, that I had to cancel a lot of what I wanted to present to aspect of art. Now, the title sounds a litle bit paradoxical, but I hope to show, that it is not exaggerated. Schlichting; Let me begin with two citation, which show the importance of learning to see and enjoying it. Schlichting; art historian Schlichting;

3 HJS6 Outline Subjects of the talk On the situation of physics teaching Reflected pitfalls Reflection vs. transparency Real deformed mirrors Summary

4 Slide 2 HJS6 Let me give you a short overview about the contents Schlichting;

5 Subjects of the talk Physically: some often overlooked aspects of the interaction between light and matter. Educationally: examination of the most obvious: learning to see, what everybody can see. Culturally: interaction between everyday life phenomena, physics and art. Goal: discussion of familiar subjects from an unfamiliar point of view; motivation by surprising, aesthetically appealing aspects of everyday life. Cause: students lack of understanding of everyday life phenomena.

6 On the situation of physics teaching One important goal of general educating schools: Physics teaching shall help students to understand and cope with their lifeworld Physics has to be related to the everyday life world. Problems 1. The physical and the common sense view are totally different. To describe the world physically means to describe it in a way we do not experience it (C.F. v. Weizsäcker). e.g. the aspect of wavelength cannot be seen directly from the quality of color 2. The everyday life world is familiar and taken for granted. Therefore, everyday life phenomena and problems have to be taken into question, familiar facts have to be experienced as something unfamiliar. 3. From the physical point of view the problems are complex. Normally students learn basic physical laws within an artificial context, but not to apply them to nonphysical situations.

7 Reflected pitfalls Glaring floors of polished stone tiles are often met in public buildings. Glare means, that the diffuse reflection is superposed by spots of specular reflection. If the specular reflection is dominating human perception may sometimes be switched to a totally new view: A flat floor may be changed to an 3Dobject. In general: Familiar phenomena suddenly become unfamiliar and make reality appear in a new light.

8 The context helps to destroy the illusion Similar illusion in Santa Maria del Fiore in Firenze

9 3D- Illusion in a pedestrian zone Julian Beevers pavement drawings

10 Switching over to the other perspective To look at specular reflecting objects as at a mirror demands to see it in a totally new way. This transition is similar to the switchingover from the one to the other view of ambivalent images or those which have been made according to the rules of perspective. Sometimes this transition has to be learnt: You have to learn to see, what everybody sees. Do you see a musician ore a young lady? Sometimes it is difficulty to switch back to the original view. Anyway, it is impossible to see both views at the same time. This procedure is accompanied by a transition from the everyday life view to the physical view.

11 When floors become mirrors Once having become attentive students more and more experience situations where things loose their color and become mirrors of the bright surroundings. Good conditions are: dark or shaded reflecting objects, light source (bright object) situated so that angle of incidence = angle of reflection, observer is not disturbed by scattered light.

12 Artistic reflections between smooth and dull The play of the artist with different reflections. Delft specular School. reflection Interieur with woman, refusing a glass of wine National Gallery diffused London. und specular reflection diffused, specular reflection and anamorphotic deformation.

13 Reflection vs. transparency

14 The relation between the light intensities matters Window panes are nearly transparent, each boundary layer reflects 4 % of the incoming light. The specular reflection dominates, if less light is coming from the other side: behind the pane it is dark, the light sources and objects in front of the window are sufficiently bright, Less light is falling through the middle window (dark side of a tree): a view into the interior is possible. To look through a window with dark interior one can use one`s own shadow.

15 Superposition

16 Puzzle of reflections

17 virtuelle Bilder Beobachter Double glazed windows double mirrors

18 Window reflections of windows The deformations of the reflected mirrors tell about the deformation of the reflection window.

19 Windows of windows a lattice of windows

20 Windows focusing light

21 Deformed mirrors All possible kinds of deformed mirrors can be found. They may be explained by the ideal forms of the concave and convex mirror. It may be recognized, that the reflection reveal and hide at the same time: they reveal the form of the reflecting object and they hide parts of it by covering it with the sight of the surroundings A classification of the types of reflections lead to and motivate a discussion of convex and concave mirrors.

22 Strait lines reveal the form of the coachwork

23 Reflections hide parts of the objects The darker the reflecting surface, the more distinct is the mirroring: diffused reflections are more and more dominated by specular reflections.

24 Bernhard Heiliger: Großer Phönix III 1992 Mirror art Inspired by reflecting coachwork

25 Water waves the kinetic variation

26 sometimes with surreal aspects

27 Multiple reflections

28 Play with optics In Science Centers as scientific toy

29 Transparent concave mirrors What s that? A kind of plasma sphere hanging in space above the lamp, slightly pulsating when going around. Spherical real image of a light- bulb within a transparent concave mirror.

30 Construction with light rays The real image of the lamp constructed within the model of light rays. M M F F Direction of vision

31 Summary The characteristic appearance of objects is determined by a superposition of specular and diffused reflection. Although by specular reflection parts of an object are covered by the images of other (bright) objects, the view (form, brilliance of transparent objects) is improved. The reflections (as image of other objects) are ignored, even if they are optical dominating. Only sometimes the perspective is changed. The reflections as such (e.g. the own mirror image) are seen only if the students attention is drawn to it the object is regarded as a mirror. The students have to learn to become aware of these background visibility and are rewarded by an interesting unfamiliar aspect of the everyday life world, by which their view is directed to the physical deep structure and in the same time, their attention is drawn to an esthetical perhaps even artistic dimension.

32 Summary But even if one is conscious of both perspectives (views), at the same time only one can be adopted. For physics teaching results the possibility and ability to recognize physical facts in the everyday life world in complex contexts. This is one important presupposition for learning to describe non physical phenomena from a physical point of view. The other way around: physics can help to detect interesting and sometimes fascinating phenomena where they are not expected and to become aware of what one can call an artistic view of the everyday life world.

33 H. Joachim Schlichting University of Muenster Germany