A shadow does not show everything about its object

Turn a familiar cutout slowly in a torch beam. The outline can narrow or change while the object remains the same, giving children a concrete reason to treat a shadow as partial information.

Ask which features remain recognisable across orientations. The changing outline can reveal why a shadow is incomplete evidence about an object.

Which features disappear from this view?

The same cutout can make a narrow shadow when turned edge-on.

Inspect the cutout. Rotate it in the beam. Compare outlines.

A shadow need not reveal the whole object's shape.

What information is missing? Use a familiar large shape.

Hold identity steady while the outline changes

Choose a large card cutout with a recognisable outline, such as a simple tree. Let children inspect the front, back and thin edge before putting it in the beam. Position a stable torch and screen, keeping the light away from faces. Ask what information the physical card provides that an outline alone might hide: colour, printed detail and thickness are useful starting examples.

Project the broad face of the tree, then slowly turn the same card toward its edge without changing its location. The shadow narrows even though no part has been cut off. Pause at two marked orientations and record the outlines. This gives the group evidence that shadow shape depends on the object's relationship to the light, not only on the object's familiar name.

Compare what is present with what is projected

Place the card beside the two recorded outlines. Ask which features can be confidently recognised in each. The branches may be obvious in one view and almost disappear in another. A child who calls the narrow outline “a stick” is making a plausible interpretation of limited visual information, rather than proving that the original object changed.

Explain that a shadow is a region receiving less light because something blocks the source. It is not a second solid tree, and it does not necessarily reproduce surface colours or markings. A hole cut through card can allow a bright area within the projected outline, providing a useful distinction between an outer boundary and all the information inside it.

Offer a mystery pair of card shapes that can each produce a similar narrow shadow. Ask whether seeing only that shadow is enough to identify which card was used. The answer can remain uncertain. This makes the activity relevant to interpreting evidence: different objects or orientations can sometimes fit the same incomplete observation.

Provide the physical cutouts for tactile exploration and describe changes aloud. Children can match prepared silhouettes rather than manipulate the light. Close by asking for one thing the shadow shows and one thing it does not establish. A careful response mentions the particular view and lighting rather than claiming shadows are always accurate pictures of objects.

Resources

• Torch investigation – Light and Shadow Major Activity — Follow the torch activity when investigating projected light and shadows.

Further reading

• CSIRO — inquiry and explicit teaching

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