4th Grade Science Lesson
Light, Reflection, and Vision: Bicycle Reflectors and Periscopes
Shared by A STEM Educator
4th GradeNGSS Phenomenon-Based4-PS4-2, 4-PS4-145 min
Learning Objective
Students will develop and use models to explain that light travels in straight lines, reflects off surfaces at predictable angles, and must enter the eye for an object to be seen (NGSS 4-PS4-2).
Lesson Overview
Students investigate how light travels in straight lines, reflects off surfaces, and must enter the eye for vision to occur, anchored in the real-world contexts of bicycle reflectors and submarine periscopes.
Materials
- Opaque cardboard box with small hole (one per group)
- Small LED flashlight (one per group)
- Flat mirror tiles (2-3 per group)
- Laser pointer or bright flashlight
- White target screen (index card or paper)
- Protractor and ruler
- Ray diagram recording sheets
- Tape and sticky putty to hold mirrors
- Cardboard tubes (for periscope model)
- Aluminum foil (as reflective surface)
- Black construction paper
- Markers and pencils
- Bicycle reflector (real or photo)
- Sticky notes
Scaffolded Task Progression
1Task 1
Floor Task — Tracing a Light Ray: Shine a flashlight at a flat mirror propped at an angle on your desk. Place a white index card (target screen) nearby. Observe where the reflected beam lands. Draw the incoming ray, the mirror surface, and the reflected ray on your recording sheet. Label: light source, mirror, reflected ray, and target screen.
[ Interactive graph / diagram — available in the full lesson ]
[ Interactive graph / diagram — available in the full lesson ]
2Task 2
**Developing Task — Angle of Reflection:** Place a mirror upright on your ray diagram sheet. Shine a flashlight so the beam hits the mirror. Use a protractor to measure the angle between the incoming beam and an imaginary line straight out from the mirror (the normal line). Then measure the angle on the other side where the light bounces. Record both angles in the table below.
```geometry
{"figureType":"triangle","angles":{"A":40,"B":90},"vertexLabels":["Incoming ray","Normal","Reflected ray"],"angleLabels":{"A":"40°","B":"90°","C":"40°"},"showAngles":true,"title":"Angle of Incidence = Angle of Reflection"}
```
What pattern do you notice between the two angles?
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