The tool below drills both from your own notes.
WeSolve+ reads the whole document and writes the questions for you
Upload your PDF, photograph your notebook, or point the camera. WeSolve+ writes questions from that material, explains why each answer is right, reads the chapter back to you as a podcast, and remembers every item you missed until you own it.
The tool below is a small browser-only tool and it is not WeSolve+: paste a few lines and text rules turn them into cards on the spot. The real app, the one that uses AI, is behind the link above.
Unit 13 optics rules, from your own notes
This is a browser-only tool, and that is all it isIt splits the text you paste by rule, and nothing else. WeSolve+ is a different thing entirely: it reads your whole PDF with AI, writes the reasoning behind every question, speaks the chapter back to you, and remembers what you missed so it can return it. Try the real app now, free!
What you paste is what gets carded. Fixed rules split the text and nothing outside it is known, which makes the paste itself the real decision.
The ray model is a contract, and its terms are short
Light travels in straight lines until a surface reflects or refracts it, and geometric optics holds while obstacles stay much larger than the wavelength. Reflection returns the ray at the incident angle; refraction bends it by the media's speeds. Every image problem in the unit is those two rules applied with a ruler.
Snell's law prices the bend, and density gives the direction
Snell's law relates angles through the indices, and the direction is memorable without algebra: entering a denser medium bends the ray toward the normal, leaving bends it away. Index questions are speed questions in disguise, since a higher index means slower light, and the exam swaps between the two phrasings deliberately.
Total internal reflection is refraction's limit case
Leaving a denser medium, the refracted ray bends away from the normal until, at the critical angle, it skims the surface; past that angle nothing exits and the boundary mirrors perfectly. Total internal reflection powers optical fibres, and the exam checks the two conditions: denser side, angle past critical.
Images are intersection stories, so tell them with three rays
A real image forms where rays actually meet and a screen can catch it; a virtual one forms where extensions meet behind the mirror or lens. The three principal rays, parallel then through focus, through centre undeviated, through focus then parallel, locate any image without algebra. Draw first: the diagram is scored, and it also checks the later arithmetic.
The equation is easy, and the signs are the exam
One over focal length equals one over object distance plus one over image distance, with magnification minus di over do. The signs carry the physics: positive di means real, negative means virtual, negative magnification means inverted, and diverging lenses take negative focal lengths. State the convention, then substitute, because a right number with an unexplained sign convinces nobody.
What to photograph for Geometric Optics
Your ray diagrams and sign tables. Related: Unit 12, photo to quiz and pricing.
Sources used on this page
- College Board, AP Physics 2: Algebra-Based
- Geometrical optics
- Snell's law
- Total internal reflection
- Mirror
- Active recall
- Spaced repetition
- Testing effect
- Forgetting curve
- Generation effect
- Judgment of learning
- Metacognition
- Desirable difficulty
- Distributed practice
- Formative assessment
- Flashcard
- Cloze test
- Multiple choice
- Test (assessment)
- Educational assessment
- Advanced Placement
- Curriculum
- Study skills
- Study guide
- Note-taking
- Overlearning
- Instructional scaffolding
- Item analysis
- Mastery learning
| Setup | Image verdict | Why |
|---|---|---|
| Object outside a converging lens focus | Real, inverted | Rays meet on the far side |
| Object inside a converging lens focus | Virtual, upright, enlarged | Extensions meet, magnifier case |
| Any object, diverging lens | Virtual, upright, reduced | Rays spread, extensions meet |
| Concave mirror, object far | Real, inverted | Rays converge in front |
| Convex mirror, any object | Virtual, upright, reduced | The security mirror case |
| Denser side, past critical angle | No transmitted ray | Total internal reflection |
What does AP Physics 2 Unit 13 cover?
The ray model: reflection, refraction under Snell's law, total internal reflection, and image formation by mirrors and lenses.
Which way does refraction bend the ray?
Toward the normal entering a denser medium, away leaving it. Higher index means slower light, and the two phrasings are interchangeable.
What are the conditions for total internal reflection?
The ray must start on the denser side and hit the boundary past the critical angle; then the surface reflects everything.
What is the difference between real and virtual images?
Real images form where rays actually meet and can land on a screen; virtual ones form where extensions meet and cannot.
What do the signs in the lens equation mean?
Positive image distance means real, negative virtual; negative magnification means inverted; diverging lenses carry negative focal lengths.
Can I build questions from my own Unit 13 notes?
Yes. Whatever you upload sets the boundary. Photograph the pages or send the chapter as a PDF and the questions stay inside it.
Last updated: 2026-08-15