SECTION I: Concept cartoons and the nature of shadows
OVERVIEW
Teacher trainees (TT’s) actively participate in a ‘specially designed’ concept cartoon session about the nature of
shadows. This subject is chosen because it is not in the standard curriculum of most students. Different didactical
strategies will be used for the different cartoons. The TT’s evaluate their own naive ideas about shadows and the
didactical possibilities of the technique (3h).
Those 3 hours take into account that for these workshops no TT is speaking his or her mother language.
LESSON PLAN
I
EXPERIMENTAL/DIDACTICAL ACTIVITIES
SECTION I
EXTRA INFO
TIME
(MIN)
0
Introduction about the project and pupil naive
ideas
Optional (only if TT’s need an overview of the
whole project). See appendix:
section I - slides introduction.ppt
section I- reference list students alternative ideas
1
Concept cartoon 1: The size of shadows
Focus on correct scientific ideas
25 min.
2
Concept cartoon 2: Shadows at night
Focus on alternative ideas and their origin
25 min.
3
Concept cartoons 3: Overlap of shadows
Focus on experimental approach
45 min.
4
Concept cartoon 4: The colour of shadows
Focus on the value of different views
60 min.
5
Overview of the didactical approaches and the
advantages and disadvantages of concept cartoons
Section I
(45 min.)
25 min.
19-10-2009
page 1 of 20
EXPERIMENTAL/DIDACTICAL ACTIVITIES SHEET I.1
NAME
CONCEPT CARTOON 1: THE SIZE OF SHADOWS
MANDATORY
PREVIOUS
KNOWLEDGE
None
GENERAL PCK
OBJECTIVES
o
o
o
o
o
o
SPECIFIC PCK
OBJECTIVES
CONTENT
KNOWLEDGE
OBJECTIVES
PEDAGOGICAL
KNOWLEDGE
TIME
NECESSARY
Search for common sense knowledge models used by TT’s or pupils.
Identify TT’s or pupils’ common reasoning strategies.
Search for TT’s or pupils naïve ideas.
Relate everyday-life phenomena with scientific models.
TT gets familiar with the method of discussing scientific ideas with a concept cartoon.
Use CC to introduce a new topic in order to get a first discussion.
In this case: the concept of shadows.
o Use CC to detect pupils’ naive ideas and understand pupils’ difficulties.
In this case with respect to the concept shadow. More specific some pupils think that
o a shadow becomes smaller when you move the object closer to the light source,
o the size of a shadow made by sunlight changes when you move.
o Use CC to see that most students are already convinced that in order to have a shadow, you
need a light source and an object.
Introduction to the concept of shadows:
o a shadow appears when light from a light source hits an object.
o the influence of the distance between light source and object.
o distant light sources create a parallel ray of light, they do not influence the size of shadows.
TT can formulate and defend a personal meaning.
TT can use group and class discussion to confront different ideas.
> 25 min
Section I / Sheet I.1
MIN.-MAX. NUMBER OF TT
19-10-2009
4-24
page 2 of 20
MATERIALS
concept cartoon (in workshopI.ppt)
SPECIAL
CONDITIONS +
POSSIBLE
OBSTACLES
o
ACTIVITIES
Class room that can be darkened
1.
2.
3.
Section I / Sheet I.1
An overhead projector or a
beamer to use as a source
of light for classical
discussion and verifying the
answers.
Show the concept cartoon.
Small period of individual reflection, each TT tries to identify himself with the propositions.
o Which idea/proposition accords yours? More answers can be chosen.
o Which do you think is or are correct?
o Is there more than one idea correct?
Don’t forget to ask “Why?” They have to think about why a certain answer is correct
or not. Maybe a proposition is only partly true. This time of reflection can be
accompanied by some small experiments by using their hands and the lights in the
classroom.
o TT can also be asked to think of a good definition of the concept shadow.
Quick scan to see what the group is thinking (e.g. by raising hands).
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4.
POSSIBLE
RESULTS
1.
Discussion with the whole group. All answers are treated. Following questions can help but
are optional.
o What happens if we move the hand closer to a light source?
o Is there still a shadow if you cover the light source completely?
o Can you think of a situation where the size of the shadow doesn’t change?
o Can you explain why?
o How can the size of a shadow made by the sun change?
My shadow is biggest when I am close to the screen.
Your shadow is biggest when you are close to the lamp.
These two answers are discussed together because they represent opposite views. It’s very unlikely
that a TT would identify himself with both ideas.
Let TT make a proposition how to check which one is correct. The answer can be found by
experiment and/or by using theory and construction.
A short experiment with the overhead projector and hands shows quickly that a shadows is bigger if
the object is closer to the light source.
It can also be explained using the fact that light travels by straight lines and that a light source
diverges light in all direction.
Section I / Sheet I.1
19-10-2009
page 4 of 20
2.
The shadow is the same no matter where you stand.
If you use the beamer, you see that this is not true. If you move your hand, the size of the shadow
changes always. An attentive TT will notice that the size of a shadow doesn’t change if you move in
the sunlight. The sun is a light source at a great distance. Light from a distant source travels
parallel. By making the same construction as before but using an parallel ray, you see that the size
doesn’t change.
3.
Your shadow will disappear when you are close to the lamp.
When you cover the light source totally, the shadow spreads itself over the whole wall or classroom.
The shadow doesn’t disappear but everything becomes shadow. Some people think that the shadow
disappears because the boundary between light and shadow is gone.
With this proposition you can start a first real discussion about the definition of the concept shadow.
You can drop the following question:
“What is the difference between covering the light source totally and putting the lights out?”
Actually, both situations have the same effect. In the first situation one speaks about shadow, in the
second one doesn’t. This starts the discussion about the nature of a shadow.
o When do we call darkness a shadow?
o Why don’t we think about shadows in all situations where there is a darkness?
Section I / Sheet I.1
19-10-2009
page 5 of 20
CONTENT CONCLUSION:
The end of this didactic activity shows the need for a good description or definition of the concept
shadow.
A first conclusion is that in order to have a shadow, you need a light source and an object.
A second conclusion can be that a shadow is the place where there is no light from the light source.
Further deepening is necessary and that will be done in the following activities.
REFERENCES
OTHER
MATERIALS
R. Casati, Shadows: Unlocking Their Secrets, from Plato to Our Time, Vintage Books USA, 2004.
Keogh B., Naylor S. Concept Cartoons In Science Education : the ConCISE Project. Millgate House
Publishers; 2002.
section I - slides.ppt
o
o
Section I / Sheet I.1
19-10-2009
page 6 of 20
EXPERIMENTAL/DIDACTICAL ACTIVITIES SHEET I.2
NAME
CONCEPT CARTOON 2: SHADOWS AT NIGHT
MANDATORY
PREVIOUS
KNOWLEDGE
none
GENERAL PCK
OBJECTIVES
o
o
o
o
o
SPECIFIC PCK
OBJECTIVES
o
Search for common sense knowledge models used by TT’s or pupils.
Identify TT’s or pupils’ common reasoning strategies.
Search for TT’s or pupils naïve ideas.
Relate everyday-life phenomena with scientific models.
Use concept cartoons to detect TT’s or pupils’ naive ideas and understand TT’s or pupils’
difficulties with respect to the concept shadow. More specific some pupils think that
o shadows are real objects;
o when there is no light, there can be no shadow.
Become aware of the logic behind different knowledge models and the fact that some models can
stand next to each other depending on the circumstances.
TT broaden their own conceptual knowledge about shadows:
o shadows look darker at night,
o the night is a shadow.
Can use group and class discussion to confront different ideas
CONTENT
KNOWLEDGE
OBJECTIVES
o
PEDAGOGICAL
KNOWLEDGE
o
TIME
NECESSARY
25 min.
Section I / Sheet I.2
MIN.-MAX. NUMBER OF TT
19-10-2009
4-24
page 7 of 20
MATERIALS
concept cartoon (in workshopI.ppt)
SPECIAL
CONDITIONS +
POSSIBLE
OBSTACLES
o
ACTIVITIES
Optional:
TT can use daily life
materials to make their
own experiments.
Class room that can be darkened.
1.
2.
3.
4.
5.
6.
7.
Section I / Sheet I.2
Optional:
o 2-6 light sources, flash
lights or light bulbs,
o an overhead projector
or a beamer can be
good light source for
class discussions.
Introduce the topic
Request a brief period of individual reflection
o Which view corresponds to yours?
Encourage small group discussion (2 to 4 TT) and invite groups to see if they can reach
consensus. When they reach consensus very rapidly, they must find reasons why
people/pupils can have another idea. Also a distinction can be made between a clouded night
and a full moon night.
Some brief feedback to see what range of views is present – perhaps a vote on the
alternatives.
Sharing outcomes of different groups and whole class discussion, including which
alternative(s) seem(s) acceptable and what further information we might need to be sure.
Draw ideas together and provide an explicit summary of the initial problem.
See if their first opinion has changed.
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page 8 of 20
POSSIBLE
RESULTS
Let’s assume that we have a dark night (clouded sky, no other light sources). Every view follows its
own logic:
1. There are shadows at night but you cannot see them
Children often have this idea because they see shadows as real physical objects. These objects will
become visible with additional light, just like any other object.
2. There are no shadows at night
Shadows are associated with the absence of light at a particular place. If there is no light, there is no
shadow.
3. Everything is shadow at night
A picture of our solar system gives a different view
on the night. There is no light in the night portion
of the earth because that portion of the earth is in
the shadow region of the Earth-Sun system. When
you approach the night this way, the night can be
seen as one big shadow. Most people do not have
this feeling because they see shadows as separate
entities.
4. Shadows look darker at night
When there is a light source during the night (e.g. the moonlight), there are shadows. A close
observation shows that those shadows look darker than during the day time. During the daytime
there is more indirect light (light of reflections on different objects and light scattered by the air
layer around the earth) reaching the shadow region. So during the night the shadows are darker.
Section I / Sheet I.2
19-10-2009
page 9 of 20
CONCLUSION:
1.
2.
REFERENCES
OTHER
MATERIALS
Ideas that seem irrelevant at first may after all be logic and worthwhile.
The conclusions we took after the first CC are still counting, even if we take the sun/earth
system.
3. The darkness of a shadow can be influenced by secondary light scources.
o R. Casati, Shadows: Unlocking Their Secrets, from Plato to Our Time, Vintage Books USA, 2004.
o Keogh B., Naylor S. Concept Cartoons In Science Education : the ConCISE Project. Millgate House
Publishers; 2002.
section I - slides.ppt
Section I / Sheet I.2
19-10-2009
page 10 of 20
EXPERIMENTAL/DIDACTICAL ACTIVITIES SHEET I.3
NAME
CONCEPT CARTOON 3: OVERLAP OF SHADOWS
MANDATORY
PREVIOUS
KNOWLEDGE
none
GENERAL PCK
OBJECTIVES
o
o
o
o
O
SPECIFIC PCK
OBJECTIVES
CONTENT
KNOWLEDGE
OBJECTIVES
o
o
o
o
Search for common sense knowledge models used by TT’s or pupils.
Identify TT’s or pupils’ common reasoning strategies.
Search for TT’s or pupils naïve ideas.
Favour modelling activities starting from experimental data.
Relate everyday-life phenomena with scientific models.
Use concept cartoons to detect pupils’ naive ideas and understand pupils’ difficulties with respect
to the concept shadow. More specific some pupils
o think that you can add the darkness of two overlapping shadows;
TT develops small and easy experiments that can simulate the simulation in picture.
TT can use those experiments to verify the ideas in the CC and draw the right conclusions.
TT use the conceptual knowledge of shadow and the conclusions of the first two CC for the
situation where 2 shadows overlap:
o not transparent object: the overlapping part is as dark as the other shadows,
o transparent object: the overlapping part is a bit darker.
Can use group and class discussion to confront different ideas.
PEDAGOGICAL
KNOWLEDGE
O
TIME
NECESSARY
45 min
Section I / Sheet I.3
MIN.-MAX. NUMBER OF TT
19-10-2009
4-24
page 11 of 20
MATERIALS
concept cartoon (in workshopI.ppt)
o
o
o
o
SPECIAL
CONDITIONS +
POSSIBLE
OBSTACLES
o
ACTIVITIES
TT can use daily life
materials to develop
experiments.
Classroom that can be darkened.
1.
2.
3.
4.
Section I / Sheet I.3
2-6 light sources, flash
lights or light bulbs, that
are fairly strong,
materials that are not
transparent,
tracing paper or
mosquito-net,
an overhead projector
and a beamer.
Introduce the topic.
Request a brief period of individual reflection.
o Which view corresponds to yours?
TT start working in small groups of 2-4 TT. With different, easy experiments they try to
investigate the overlap of shadows.
It is important that they simulate the 2 situations: not transparent and transparent.
The outcomes of all the groups are presented to the whole group. Because of the complex
situation, the previous definition of the concept shadow may have to be reconsidered and
broadened.
19-10-2009
page 12 of 20
POSSIBLE
RESULTS
With this concept cartoon there has to be made a difference between 2 situations, the last a bit
more complex than the first one.
1. The shadow is twice as dark where the shadows overlap.
When people choose this proposition, they see a shadow as an object. If you add two shadows, you
get a new shadow that is twice as dark. They forget that if there is a shadow it just means that there
is (almost) no light in that space. “Almost no” light, because there is always some indirect light we
have to take into account.
2.
The shadow is just as dark where the shadows overlap.
If shadow is defined as the absence of light of the light source, it is obvious that you can take away
the light from that source only once. If it’s gone than you can’t take any more light from the light
source away. So the place where two shadows overlap is as dark as the other shadows. The
experiment makes it clear if you overlap the shadows of 2 objects that are not transparent.
3. This shadow is a bit darker but not twice as dark.
If a TT chooses for this answer, he or she has a more complex situation in mind. The situation drawn
in the cartoon is one with trees. Trees are a little transparent, depending on the density and
placement of the leaves. Where the shadows of two trees overlap, the shadow will be a bit darker.
The leaves of the first tree blocs of only some light. The rest of the light passes through the leaves
of the first tree but can be hold back by the leaves of the second tree. Because the overlapping
shadow is caused by a double amount of leaves, the shadow is a bit darker.
If the experiment from answer 2 is repeated but now with transparent materials like tracing paper or
a piece of a mosquito-net, this answer will become visual.
Section I / Sheet I.3
19-10-2009
page 13 of 20
CONCLUSION:
De previous description of the concept shadow has to be changed. A shadow appears when the light
from a light source is totally or partially stopped by an object.
In this CC it is for the first time that the concepts of light and shadow meet. In the last experiment
you can ask yourself the question:
“What do we call the spot behind a transparent object? Light or shadow?”
REFERENCES
OTHER
MATERIALS
We will discuss this question in the next CC.
o R. Casati, Shadows: Unlocking Their Secrets, from Plato to Our Time, Vintage Books USA, 2004.
o Keogh B., Naylor S. Concept Cartoons In Science Education : the ConCISE Project. Millgate House
Publishers; 2002.
section I - slides.ppt
Section I / Sheet I.3
19-10-2009
page 14 of 20
EXPERIMENTAL/DIDACTICAL ACTIVITIES SHEET I.4
NAME
CONCEPT CARTOON 4: THE COLOUR OF SHADOWS
MANDATORY
PREVIOUS
KNOWLEDGE
none
GENERAL PCK
OBJECTIVES
o
o
o
o
o
o
SPECIFIC PCK
OBJECTIVES
o
o
CONTENT
KNOWLEDGE
OBJECTIVES
o
o
Search for common sense knowledge models used by TT’s or pupils.
Identify TT’s or pupils’ common reasoning strategies.
Search for TT’s or pupils naïve ideas.
Favour modelling activities starting from experimental data.
Relate everyday-life phenomena with scientific models.
Use concept cartoons to detect pupils’ naive ideas and understand students’ difficulties with
respect to the concept shadow. More specific some pupils
o think that shadows are black;
o confuse shadow and light
Use concept cartoons to get learners to experience uncertainty and cognitive conflict.
Find valuable aspects in different views, depending on the definition used and the conditions
different conceptual views can be correct.
Use experiments to deal with cognitive conflicts and to obtain valuable conclusions
Broaden their own conceptual knowledge about shadows:
o most shadows have colours;
o find a realistic definition of shadows;
o understand that the conceptual difference between shadows and light is small.
Can use group and class discussion to confront different ideas
PEDAGOGICAL
KNOWLEDGE
o
TIME
NECESSARY
> 60 min.
SPECIAL
CONDITIONS +
POSSIBLE
OBSTACLES
Class room that can be darkened.
Section I / Sheet I.4
MIN.-MAX. NUMBER OF TT
19-10-2009
4-24
page 15 of 20
MATERIALS
concept cartoon (in workshopI.ppt)
Optional:
o 2-6 light sources, flash
lights or light bulbs,
o an overhead projector or
a beamer can be good
light source for class
discussions.
Optional:
o 2-6 sets of coloured
paper and coloured
plastic
o if possible fixed on a
small wooden block.
TT can use daily life
materials like plastic maps,
sun light, coloured papers,
etc to make their own
experiments.
ACTIVITIES
1.
2.
3.
4.
5.
6.
Section I / Sheet I.4
Introduce the topic
Request a brief period of individual reflection
o Which view corresponds to yours?
Encourage small group discussion (2 to 4 TT) and invite groups to see if they can reach
consensus. When they reach consensus very rapidly, state that the so called ‘wrong’ views
can also be correct. They have to figure out under which conditions.
Some brief feedback to see what range of views is present – perhaps a vote on the
alternatives.
Class or group discussion of how we could investigate the situation to find out which
alternative(s) are acceptable and under which conditions. If necessary, enrich the discussion
with the following questions?
o What is the definition of shadows? Is this definition applicable to daily life shadows? Can
we make the definition more general?
o Is the shadow of a person on a coloured background (like grass) black?
o When there is only red light in a room. Will the shadows be red?
o Do you understand why shadows on white snow look blue?
Small group enquiry.
19-10-2009
page 16 of 20
7.
Share outcomes of enquiry and whole class discussion, including which alternative(s) seem(s)
acceptable and what further information we might need to be sure.
8. Draw ideas together and provide an explicit summary of the initial problem, the enquiry, the
outcome and what has been learnt from the enquiry.
9. Consider how the learners’ views might have been changed and what has led the change in
their ideas.
10. Extra: Answer the extra questions from 5.
11. Extra: Try to create other coloured shadows
POSSIBLE
RESULTS
Shadows are mostly defined as the region where the direct light of the light source can not reach.
Because people focus on only one light source, the idea of black shadows is widespread.
But the extreme case where there is absolutely no light reaching the shadow region is a rare
phenomenon. Look at the shadows around you, and you will see the colour of the substrate (e.g. on
grass, the dark green shadows). This means that there is still light that reaches the shadow region.
This can be light from multiple reflections (even blue light reflected by the sky) or from other light
sources.
Most people will say that the orange ‘spot’ behind the orange filter has nothing to do with a coloured
shadow, but is coloured light. This is only partly correct because the shadow view also makes sense.
The filter stops all the frequencies of the light beside the orange frequencies, so creating a shadow
for the non orange frequencies. So shadows can be light and light can be a shadow.
Section I / Sheet I.4
19-10-2009
page 17 of 20
CONCLUSION:
REFERENCES
OTHER
MATERIALS
1.
All shadows are black: Is only correct when there is only one light source and no indirect
light.
2.
There is an orange shadow behind the orange card: This view is often related to a confusion
between shadow and light. But the shadow can have an orange shade when there is sufficient
indirect light. Then the reflected light on the orange card can reach the shadow region.
3.
The orange glass has an orange shadow: The orange spot is the shadow of all the non-orange
light frequencies.
4.
There is no shadow behind the glass only light: Is correct when you only focus on the point of
view of the light. The filter lets the orange frequencies of the light pass, giving a light spot.
R. Casati, Shadows: Unlocking Their Secrets, from Plato to Our Time, Vintage Books USA, 2004.
Keogh B., Naylor S. Concept Cartoons In Science Education : the ConCISE Project. Millgate House
Publishers; 2002.
section I - slides.ppt
o
o
Section I / Sheet I.4
19-10-2009
page 18 of 20
EXPERIMENTAL/DIDACTICAL ACTIVITIES SHEET I.5
NAME
OVERVIEW OF DIDACTICAL APPROACHES AND THE USE OF CC IN LESSONS.
MANDATORY
PREVIOUS
KNOWLEDGE
none
GENERAL PCK
OBJECTIVES
o Relate everyday-life phenomena with scientific models.
o Favour modelling activities starting from experimental data.
o Search for common sense knowledge models used by TT’s or pupils.
o Identify TT’s or pupils’ common reasoning strategies.
o Search for TT’s or pupils naïve ideas.
none
SPECIFIC PCK
OBJECTIVES
CONTENT
KNOWLEDGE
OBJECTIVES
TT’s summarize the workshop and their experience so that the general way of dealing with CC
becomes clear.
PEDAGOGICAL
KNOWLEDGE
o
o
TIME
NECESSARY
25 min
SPECIAL
CONDITIONS +
POSSIBLE
OBSTACLES
none
MATERIALS
none
ACTIVITIES
o During this activity the experiences from TT during the first 4 activities are summarised.
o They learn how to use CC in classroom conditions.
For this activity we refer to Workshop1.ppt
The goal of this whole workshop is
o to get TT’s enthusiastic about CC.
o to make them eager to discover more cartoons.
o to let them feel that CC is a good method to use is classroom conditions.
POSSIBLE
RESULTS
Section I / Sheet I.5
TT can summarize how he/she has experienced the workshop.
TT can listen to other TT’s and can give comments based on his/her experience.
MIN.-MAX. NUMBER OF TT
19-10-2009
4-24
page 19 of 20
REFERENCES
OTHER
MATERIALS
R. Casati, Shadows: Unlocking Their Secrets, from Plato to Our Time, Vintage Books USA, 2004.
Keogh B., Naylor S. Concept Cartoons In Science Education : the ConCISE Project. Millgate House
Publishers; 2002.
o Other references on our Reference list students alternative ideas, in attachment.
section I - slides.ppt
o
o
Section I / Sheet I.5
19-10-2009
page 20 of 20