Laser Light Wave Patterns Experiment for Kids
A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.
Materials Needed
- • 532 nm green laser diode pointer (class 2 or 3R) (1 unit)
- • 50:50 optical beam splitter cube (or thin glass microscope slide) (1 unit)
- • Front-surface flat mirrors with fine-pitch tilt adjustment mounts (2 units)
- • Heavy rigid aluminum breadboard or solid wood block (approx. 30x30 cm) (1 base)
- • Diverging lens (or webcam lens) and white projection card (1 set)
Pro Tips
- → Albert Michelson used this instrument to measure the speed of light and disprove the luminiferous ether.
- → A laser beam hits a 50:50 beam splitter: half reflects to Mirror 1 and half passes to Mirror 2.
- → When the two reflected beams recombine on a screen, their overlapping wave crests and troughs create concentric interference rings.
- → Gently touching the base plate shifts the optical path by nanometers, causing the interference rings to expand and contract.
Safety First
Never look directly into the laser beam or reflective mirror paths; terminate beam on a matte projection screen.
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Step-by-Step Instructions
Step 1
Anchor a 532 nm green laser pointer and a 50:50 beam splitter cube onto a heavy, rigid base plate in a darkened room.
Step 2
Mount two plane mirrors perpendicular to each other so each reflected beam returns directly to the beam splitter face.
Step 3
Expand the recombined exit beam through a small convex lens onto a white wall screen, adjusting mirror tilt screws until circular interference fringes appear.
Step 4
Observe the concentric bright and dark fringe rings shift and breathe when you speak softly or warm the air in one arm.