Locate a virtual image without sending light behind a mirror
A plane-mirror image can be located by tracing physical reflected rays backward as straight-line extensions. The reflected light stays on the object side, but an observer interprets the diverging rays as coming from a point behind the mirror. That apparent point is a virtual image. Dashed extensions are a geometric construction, not rays passing through the reflecting surface.
Learning outcome: Retain object distances 20 and 40 cm at the same height. Follow each physical segment and its dashed backward extension. Compare image distance, height and the object-to-image separation.
Starting recap
Define normal angles and signed object/image distances. Distinguish actual ray intersections from backward extensions, and keep the focal/critical boundaries explicit rather than forcing a finite answer.
All lessons are open directly. Your saved experiments remain when you leave and return.
Try
An object 30 cm in front of the mirror has i=−30 cm, height unchanged and M=+1. Object-to-image separation is 60 cm. If the object moves 10 cm farther away, the separation becomes 80 cm.
Open the experimentPredict
If a virtual image is visible, must physical reflected rays pass through its apparent location?
Experiment
Retain object distances 20 and 40 cm at the same height. Follow each physical segment and its dashed backward extension. Compare image distance, height and the object-to-image separation.
Locate a plane-mirror image by backward extensions
Worked teaching model · synthetic values · Vertical plane mirror x=0; object on left, rays travel toward mirror then reflect left. Image behind mirror is virtual, equal height and equal distance. Dashed lines are backward extensions, not light traveling through the mirror.
Reset keeps your prediction, captures and practice history.
Physical ray direction follows its listed first coordinate to last coordinate. Dashed lines are not extra propagating rays. Display scale changes between settings; within the diagram both axes use the same scale.
| Segment | Coordinates in listed direction | Type |
|---|---|---|
| Incoming ray at mirror height 0 | (-30, 6) → (0, 0) | Physical ray |
| Reflected ray at mirror height 0 | (0, 0) → (-30, -6) | Physical ray |
| Backward extension at mirror height 0 | (0, 0) → (30, 6) | Extension / construction |
| Incoming ray at mirror height 3 | (-30, 6) → (0, 3) | Physical ray |
| Reflected ray at mirror height 3 | (0, 3) → (-30, 0) | Physical ray |
| Backward extension at mirror height 3 | (0, 3) → (30, 6) | Extension / construction |
| Plane mirror | (0, -6) → (0, 12) | Extension / construction |
| Quantity | Value | Unit |
|---|---|---|
| Signed image distance | -30 | cm |
| Image height | 6 | cm |
| Magnification | 1 | ratio |
Accessible plot coordinates
Backward extensions meet behind the mirror, while reflected light remains in front.
Positive object distance is in front of the mirror; signed image distance is negative for this virtual image. A screen behind an opaque mirror does not capture this image. The virtual image can still be seen by an observer receiving reflected rays.
Backward extensions meet behind the mirror, while reflected light remains in front.
Positive object distance is in front of the mirror; signed image distance is negative for this virtual image. A screen behind an opaque mirror does not capture this image. The virtual image can still be seen by an observer receiving reflected rays.
Captures preserve recipes and replay their calculated results. They are synthetic model evidence, not physical measurements.
Understand
Apply
Public practice checks a specific claim. It does not establish independent mastery.
Explain why no sharp image on a screen behind the mirror can be the correct prediction rather than a measurement failure.
Continue
Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.
Skipping retains experiments and awards no mastery.
Save a science backup or import one
Science work is stored locally in this browser, separately from mathematics and AI. It does not sync automatically. Use this science-only backup; this checkout's older all-subject export does not include science.
A legacy file is available only when the complete snapshot fits the 36 MB limit. For larger snapshots, prepare a complete file set below; never discard notebooks to make a smaller file.
Matching imported notebook drafts replace their current drafts. Omitted lessons and known first attempts remain. Export your current work first if you want to retain both drafts.
Complete file sets and course backups
A file set can hold more work than one science file. Keep its manifest and every part together. Each file is limited to 36 MB. This format needs this version of LearnAI or a compatible newer version; older versions can use only the legacy single-file backup above.
The set includes every saved science course and global continuation at this moment. Later edits need a new export. A conflicting tab exports its own visible work, which may differ from saved work in another tab.
0 file(s) selected. File order and filenames do not determine identity. Missing, changed or conflicting parts block the entire restore; no good part is applied by itself.
Science storage: loading. No account or remote computation is required.