Visible Light
Light, Sound and Waves

Selecting and developing activities for seeing things

Classroom Activity for 5-11 Supporting Physics Teaching

Teacher Tip: Based on the Physics Narrative and the Teaching and Learning Issues

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 Narrative to find these lines of thinking worked out and then look in the Teaching Approaches 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.

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