Ray-Tracing Optical Plano-Convex Lens Bench
A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.
Materials Needed
- • 1-meter wooden or metal ruler (1 unit)
- • Double-convex or plano-convex optical glass lens (approx. 10 cm focal length) (1 unit)
- • White cardstock (projection screen, 10x15 cm) (1 piece)
- • Small LED keylight or tea-light candle (1 unit)
- • Modeling clay (for sliding base mounts) (1 block)
Pro Tips
- → Mount the lens, card screen, and light source onto modeling clay stands so they slide smoothly along a flat meter stick.
- → Slide the screen back and forth until the projected image of the flame or flashlight grid snaps into sharp focus.
- → Measure object distance and image distance, then use the Thin Lens Equation to calculate the true focal length of the glass lens.
Safety First
Adult supervision required if using a small tea-light candle as the object light source.
How was this activity?
Your anonymous feedback helps us recommend better activities.
Step-by-Step Instructions
Step 1
Anchor a convex lens, a small LED light source, and a white cardstock screen into clay blocks and align them along a 1-meter stick.
Step 2
Position the light source 30 cm from the lens and slide the cardstock screen until the projected image becomes sharp.
Step 3
Record object distance (do) and image distance (di) in millimeters, observing that the focused image is upside-down.
Step 4
Calculate the lens focal length using the formula 1/f = 1/do + 1/di and repeat at two other distances to confirm the result.