Why Do Shadows Change Size and Shape?

Why do shadows change size and shape?

Lab Activity

4-9.6 Recognize that opaque materials cast shadows, and predict changes in the size and location of shadows resulting from the movement of a light source or from the movement of a shade-casting object.

Skills:

4–2 Identify patterns and order in objects and events studied; and record observations, using pictures, words and charts, with guidance in the construction of charts; and make predictions and generalizations, based on observations.

Reflect and Interpret - state an inference, based on observations

Materials:

·  overhead projectors

·  whiteboard or chart paper

·  markers

·  metre sticks or measuring tape

Related Video Clips (use to introduce the concepts that will be explored in the lab – if the Youtube links are outdated, just search the video title on Youtube):

Focus question for viewing: How did they do that???

·  Cool Hand Shadows - http://www.youtube.com/watch?v=ZUIDXTG8Xds&feature=related

·  Pilobolus Shadow Dancing (Hyundai Commercial): http://www.youtube.com/watch?v=elWf8nI6ivw&feature=related

·  Pilobolus Shadow Dancing (Royal Blackpool Variety Performance): http://www.youtube.com/watch?v=eg3Pe6MK24o&feature=related

Procedure – Movement of a shade-casting object:

1.  Students form groups of 3 and collect their materials.

2.  Students position their overhead projector to shine light on the whiteboard OR in front of a piece of chart paper taped onto the wall.

3.  One student makes a shadow puppet shape with their hand and stands close to the overhead projector. One student measures/records the distance their partner is standing from the projector, while the remaining student traces the shadow onto the whiteboard/paper.

4.  The shadow puppet student takes one step back, away from the projector – again, one student measures/records the distance, while the remaining student traces the shadow shape onto the whiteboard/paper.

5.  The process is repeated a third time, with the shadow puppet student taking one last step back. Sample:

Procedure – Movement of light source:

1.  Repeat the above procedure, but the shadow puppet student stands in one place, and the light source (overhead projector) moves.