Where does light meet?
Move an object and change a converging lens. Then explore a simplified eye.
Thin-lens model: 1/f = 1/dₒ + 1/dᵢ. Distances are in model units. For the same material, the drawn lens becomes more curved at shorter focal lengths and flatter at longer ones. Its outline is illustrative, not a calculated lens profile. The eye has a fixed model retina, an adjustable lens, and no cornea. It does not calculate prescriptions.
Read more: OpenStax · Thin lenses ↗Small cell. Big difference.
Grow a spherical cell and compare how its outside and inside scale.
A perfect sphere: area = 4πr², volume = 4πr³/3. Real cells have different shapes, structures, and ways to move materials. This model illustrates geometry rather than a maximum viable cell size.
Read more: OpenStax · Surface area and volume ↗Follow a signal.
Trigger a signal and follow a conceptual route through two neurons.
A route illustration, not an electrical simulation. The colored dot represents progress. Real action potentials, neurotransmitters, inhibition, and timing are more complex; playback speed is not biological speed.
Read more: OpenStax · Nervous tissue ↗A journey around the body.
Follow one marker through the heart, lungs, and body. Select a stop to learn its role.
A route map, not anatomical positioning or a flow calculation. Red means relatively oxygen-rich and blue relatively oxygen-poor; blood is never blue. Marker motion and timing are illustrative.
Read more: NIH · Blood flow through the heart ↗Make room for a breath.
Pull the model diaphragm downward and watch the space and lungs change.
A simplified bell-jar analogy. Lowering the diaphragm expands the chest; a transient pressure difference draws air inward. At the end of a breath, pressure equalizes. Lung elasticity, ribs, and pleural mechanics are not calculated.
Read more: OpenStax · The process of breathing ↗See the shape of a sound.
Adjust frequency and amplitude. Compare the traces over the same time window.
An ideal sine-wave pressure trace over time, not the physical shape of moving air. Frequency relates to pitch; greater amplitude generally means greater loudness, but perception also depends on frequency and the listener. No audio plays.
Read more: OpenStax · Sound frequency ↗A closer look at a cell.
Zoom the illustration, adjust focus, and select a structure to explore.
An illustrated animal-cell model, not a microscopy photograph. Zoom does not add resolving power. Structures are exaggerated and visible here even when a classroom light microscope would not distinguish them.
Read more: OpenStax · Eukaryotic cells ↗Chance has a pattern.
Choose two hypothetical parents. Compare expected probabilities with random offspring.
One hypothetical gene with two alleles, equal allele transmission, and complete dominance. A is dominant to a in this model. Dominant does not mean better or more common. Most human traits are more complex; this is not a prediction about anyone’s family.
Read more: NIH · Mendelian inheritance ↗