ConceptOptics
← All conceptsLenses (foundational)
thin-lens equation 1/f=1/u+1/v, magnification M=hi/ho=v/u, real vs virtual images
9 ways this goes wrong. Each one is a named misconception the questions are built to catch.
- Converging/diverging lens swappedTreats a concave (diverging) lens as converging, or assigns a positive focal length to a diverging lens.→
- Diverging lens forms real imageExpects a single diverging lens to produce a real image of a real object, when it only forms a virtual, upright, reduced one.→
- Image position misjudgedPlaces the image at the wrong location for an object inside versus outside the focal length of a converging lens.→
- Lens focal-length sign ignoredUses a positive focal length for a diverging lens (or ignores sign conventions for the image distance), so a virtual image is treated as real.→
- Lens image always invertedAssumes a converging lens always inverts the image, ignoring the upright virtual image when the object is within the focal length.→
- Magnification ratio invertedComputes magnification as u/v or object-over-image height instead of M=hi/ho=v/u.→
- Magnification sign ignoredDrops the sign of the magnification, so an inverted (negative M) image is reported as upright.→
- Thin-lens equation misusedAdds object and image distances directly (or sets f=u+v) instead of combining reciprocals in 1/f=1/u+1/v.→
- Virtual image labeled realCalls the enlarged upright image from an object inside the focal length real instead of virtual.→
