Activity 01
Demonstration: Changing Shadow Sizes
Provide torches, objects like toys, and white screens. Students predict then test how moving the object closer to the light enlarges shadows and farther away shrinks them. Record measurements of shadow heights at three distances for comparison.
Why do shadows have the same shape as the object blocking the light?
Facilitation TipDuring the Demonstration: Changing Shadow Sizes, move the torch slowly while students observe the shadow edge to emphasize that light moves in unbroken straight lines.
What to look forProvide students with a torch, a small object, and a piece of paper. Ask them to set up an experiment to create a shadow and then adjust the position of the torch to make the shadow larger. Have them draw their setup and label the light source, object, and shadow.
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Activity 02
Pairs: Mirror Reflection Tracing
Pairs use torches and mirrors on paper. Shine light at different angles, trace incoming and reflected rays with pencils. Measure angles to confirm equal bounce, then draw virtual image positions behind the mirror.
How does a mirror show you your reflection?
Facilitation TipFor Mirror Reflection Tracing, provide each pair with a protractor and colored pencils to clearly mark angles of incidence and reflection.
What to look forPose the question: 'If light travels in straight lines, why does the shadow of a tree look curved at the top?' Facilitate a class discussion, guiding students to consider the shape of the light source (the sun) and how it affects the shadow's edges.
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Activity 03
Whole Class: Straight-Line Light Relay
Arrange students in a line holding cards with holes. Pass torch light end-to-end; block one hole to show light stops. Discuss why bending paths fail, reinforcing straight travel.
Can you make a shadow bigger or smaller? How?
Facilitation TipIn Straight-Line Light Relay, assign each student a specific torch position so groups test multiple angles systematically.
What to look forStudents draw a simple diagram showing a light source, an object, and a mirror. They should then draw at least two light rays from the object reflecting off the mirror and reaching an observer's eye, explaining in one sentence how the mirror allows them to see the object.
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Activity 04
Individual: Pinhole Shadow Viewer
Students make pinhole viewers from boxes and foil. Point at light sources outdoors to project inverted shadows. Note straight paths by observing sharp edges and positions.
Why do shadows have the same shape as the object blocking the light?
Facilitation TipFor Pinhole Shadow Viewer, have students hold the paper steady while moving the screen to see how the pinhole projects a clear image.
What to look forProvide students with a torch, a small object, and a piece of paper. Ask them to set up an experiment to create a shadow and then adjust the position of the torch to make the shadow larger. Have them draw their setup and label the light source, object, and shadow.
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Generate Complete Lesson→A few notes on teaching this unit
Teach this topic by starting with concrete, observable phenomena before moving to diagrams. Use guided inquiry so students articulate rules ('shadows grow when the object moves closer to the light') rather than receive them. Avoid over-explaining; let students test their own ideas with materials first. Research shows students retain concepts better when they resolve contradictions through evidence.
Successful learning looks like students accurately predicting how shadow size changes with light position, precisely tracing reflected rays with protractors, and explaining why mirrors show images without light passing through. They should connect observations to the core idea of straight-line light travel.
Watch Out for These Misconceptions
During Demonstration: Changing Shadow Sizes, watch for students who believe shadows grow because light bends around objects. After the activity, ask them to trace the torch beam with their finger to confirm straight-line travel.
During Mirror Reflection Tracing, students often think mirrors show images from behind the glass. After tracing rays, have them place a small sticker on the mirror's surface to prove no light passes through.
During Demonstration: Changing Shadow Sizes, watch for students who assume shadows always match object size exactly. After measuring shadows at different distances, ask them to sketch revised predictions.
During Pinhole Shadow Viewer, students may think the pinhole creates light. After observing the projected image, ask them to trace the light path from the torch through the pinhole to the screen.
During Mirror Reflection Tracing, watch for students who think mirrors show real images. After completing ray diagrams, have them hold a small object against the mirror's back to see it doesn't appear there.
During Straight-Line Light Relay, students may think light can curve. After testing multiple torch positions, ask them to describe why the shadow edge remains sharp regardless of hand position.
Methods used in this brief