Selecting and developing activities for seeing things
Classroom Activity
for 5-11
Ideas to emphasise here
- Construct the source-medium-detector model
- Show illumination as a process where something travels
- Build a helpful model of how illumination diminishes
- Emphasise that there is a finite trip time from source to detector
- Draw out the role of light in enabling seeing
- Bring to mind the role of reflection in seeing luminous objects
- Always explicitly accounting for reductions in brightness
- The physical aspect of the transmission of light
- Light is emitted by luminous objects
- Light travels in straight lines
- Objects are transparent, translucent or opaque
- Objects that are opaque cast shadows
- We only see non-luminous objects when light bounces off them
- Sometimes, if the object is shiny, this bouncing can form an image (mirrors)
- Light is detected by our eyes
- Light travelling is the spreading of the vibrations
- Link reductions in intensity with distance from the source
- Link delays in hearing sounds compared to seeing sights to the trip time of propagation from the source
- That light travels through a vacuum (from the Sun and other stars)
Teacher Tip: Work through the Physics Narratives to find these lines of thinking worked out and then look in the Classroom Activities for some examples of activities.
Strategies for supporting learning
- Identify source and detector
- Separate luminous from non-luminous
- Draw out children's ideas about seeing
- Connect seeing to the source-medium-detector model
- Build an explicit model of seeing
- Organise what children have observed into a coherent whole
- Build three-dimension models where illumination is important
- Draw out what children believe about the Earth-Moon-Sun system and how this is related to everyday phenomena
- Avoid restricting the idea of reflection to shiny surfaces
- Reinforce the role of reflection in seeing
- Connect seeing to both specular and diffuse reflections
- Show clear examples of the phenomena
- Introduce a wide range of surfaces from which reflection happens
- Put the source–medium-detector model to use; note the lack of tangible medium
- Connect light sources (luminous objects) to how we detect them
- Connect seeing to the source-medium-detector model
- Separate the luminous object that generates the vibration from the propagation of the vibration, which is also a movement
- Emphasising that all lights have a source
- Emphasising that we only see non-luminous objects when light bounces off them
- Tracing the chain from source to detector, via object, often
- Connect human vision to what other species can see (for example snakes can see in IR and insects in UV)
- Link each light seen back to the source, via the object it bounces off
- Look at different early models of seeing to see which ones fit the evidence of our experiments.
Teacher Tip: These are all related to findings about children's ideas from research. The teaching activities will provide some suggestions. So will colleagues, near and far.
Avoid these
- Speaking or acting as if light was just there
- Assuming that how we see is well understood
- Assuming that seeing is all accounted for by the physics
- Conflating rays (the theoretical construct) with light beams (the physical)
- Running together what is noticed and recorded with what is modelled
- Restricting examples of reflection to only, or mostly, shiny surfaces
- Replacing experiences of real and interesting phenomena with a series of ad hoc memorised rules
- Not showing how an understanding of simple situations is linked to a wide variety of phenomena in the lived-in world
- Introducing the technical term 'ray'
- Using specious energy descriptions
- Drawing or showing transverse waveforms
- Asserting that light is a wave without clarifying explanation of the idea of a wave – this is hard
- Introducing wavelength, frequency, or energy of light
Teacher Tip: These difficulties are distilled from: the research findings; the practice of well-connected teachers with expertise; issues intrinsic to representing the physics well.