Visible Light
Light Sound and Waves

Selecting and developing activities for seeing things

Classroom Activity for 5-11 Supporting Physics Teaching

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.

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