A sequence to develop ideas about seeing
Classroom Activity for 5-11
Based on the Physics Narrative and the Teaching and Learning Issues
Meeting reality: valuable experiences
Seeing is a very significant sense to humans, and some images evoke strong emotional responses. The physicality of the light is really important, both of making connections to the underpinning waves and for establishing a context for the learning and the emotional hooks.
- noticing lights from many different sources
- using a large dark space to explore
not-seeing in the dark
- exploring collections of sources that make lights of different brightness
- tracing out the paths of light from source to detector, via other objects
As many of these as possible should be direct physical experiences, rather than mediated through video clips. This locates the learning in the lived-in world of the child, and grounds the learning in specific physical circumstances.
A sequence for developing the idea
This is a suggested sequence of activities, so a repertoire, on which to draw as you decide on a sequence to best suit the children in your own situation.
The ideas are developed in the Physics Narrative.
There are a large number of light sources in the everyday lived in world, and this activity begins bring them to children's notice. it can also be used to use the general idea of a light source.
This activity compares natural and man-made lights, and begins to develop ways of describing the sources, and of thinking about how we come to see.
This is something of an extension activity, building on the noticing of light sources.
This is in many ways the core activity where the focus strongly on the ways in which we see. The source-medium-detector model is at the core of this activity.
An absence of light means we cannot see. Many children will not have experienced a total absence of light and may therefore not appreciate that some light is essential to seeing. This experience presents an opportunity to provide the experience and to work on the incorrect idea.
Where there is no light, we cannot see. If light from a source does not travels to a particular location then we will not be able to see the source. Shadows are such locations. Here is the simple way of introducing shadows.
Light and darkness are extremes, but there are different brightnesses between total absence of light and very bright sunlight. Using a data logger may enable you to tell interesting story about the variation in brightness – but only if you choose an interesting place to make your measurement.
Sharp shadows rely on light travelling in straight lines and therefore provides a very good contacts were beginning to talk about how you can decide where there are shadows and where there are not. Such an approach also begins the discussion about light travelling in straight lines, which is assumed by this activity.
This is a challenging activity out of which interesting discussions might grow.
Messages from research and practice: specific tripwires for this idea
To illuminate an object requires a source from which the light travels. If you can see that illuminated object, then the light has bounced off the object and into your eye. So the journey is essential to seeing, and tracing out this journey is a common theme – and common difficulty – in teaching this topic. Many of the highlighted challenges are concerned with this journey from source to detector.
Light must travel from its source to the detector: or it will not be detected. Much of the language that we use about lighting obscures this essential travelling, and so children quite often do not think of light is travelling from source to detector.
Children have a number of different ideas on how we see, and it's a good idea to be aware of these in order to be able to challenge these ideas explicitly. In this way you will give children an opportunity to correct their ideas.
It is rather common for children to think the light gets used up on its way from the source. So it's worth challenging this particular idea head on.
For you to be able to see one thing light must travel from our thing to your eye. If the thing is not luminous ( so it does not glow, so providing its own lighting), then light must reflect from the thing for you to see it. So is not only mirrors that reflect – in fact these are a rather special form of reflection.
These challenges and some suggestions for working with them are more fully explained in the Teaching and Learning Issues.
Representing and reasoning: doing physics
The journey the light takes in order to get from what you've seen to your eye is the idea at the centre of this topic. To see something is to receive light in your eye from that thing. No lighting: no sighting. Everything else is secondary. so building and using the source-detector representation is the major task of this topic.
To see something is to have light travel from our thing to your eye.
This pair of expositions are linked, in that the formation of shadows is a strong piece of evidence for light travelling in straight lines. Although this is not formally required for the children at this stage it is useful to have in your mind.
Every thing that is not luminous requires light to reflect from it in order to be seen. Therefore anything that can be seen must reflect light
- light travels from a source to your eye, if you can see the source
- if you obstruct the route, then you get a shadow
- if no light into your eye from the source, then you cannot see it
- seeing many things relies on reflected light
Find out more from the Physics Narrative.