Key idea
Thin lenses
Lentille mince : 1/f = 1/dₒ + 1/dᵢ
Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.
Thin lenses
The key idea
A thin-lens model relates object distance, image distance and focal length. Converging and diverging lenses can form very different images depending on geometry.
Why it matters
Ray diagrams are not decoration: they encode the geometry that predicts where an image forms and whether it is real, virtual, upright or inverted.
A picture to remember
Key idea
Thin lenses
Guided example
Thin lenses
Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.
Put it into practice
Thin lenses
Choose a concrete case linked to Thin lenses. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.