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Light & Lens Explorer

Switch between reflection, refraction, total internal reflection, and converging-lens modes to reason directly from ray diagrams.

  • SEC G3 Physics 2027
Learning goals
  • Use the normal, angle of incidence and angle of reflection
  • Apply the law of reflection in constructions, measurements and calculations
  • Use the normal, angle of incidence and angle of refraction
  • Apply sin i divided by sin r as a constant for a fixed pair of media
  • Define refractive index as vacuum light speed divided by medium light speed

Interactive stageLive model

Loading the interactive model…The interactive model did not load. Try again reloads this page; the explanation and worked content here are still available.

Worked reflection ray diagramA ray meets a horizontal mirror at 38 degrees from the dashed normal and reflects at the same angle on the other side.Reflection: measure from the normalincident i = 38°reflected r = 38°normalmirrorThe two angles are equal and use the dashed normal, not the mirror surface.
Static worked state for the default setup. The table keeps the other three optics relationships available without colour, dragging, or JavaScript.
Representative states covered by this explorer
ModeInputsRelationship or outcome
Reflectioni = 38°r = 38°, measured from the normal
Refractioni = 38°, n = 1.50r = 24.2°; emergent ray stays parallel
Critical angle / TIRi = 38°, n = 1.50c = 41.8°; refracts out into air
Converging lensu = 18 cm, f = 10 cmv = 22.5 cm; real, inverted, magnified

Loading the optional interactive ray geometry. The complete static worked state remains available until it is ready.

Change one variable at a time and watch the model respond.

Diagram setup

Mode and main controls
38°
18 cm
More controls
Material and lens values
1.50
10 cm

Ray-diagram checkpoint

What to notice:

Prediction target:

      Practice run

      Choose a mode and checkpoint count when you want scoring.

      Run mode
      Try Waves Quiz

      Choose your checkpoint count for guided or challenge mode.

      Study lensUse normal lines and ray paths to explain reflection and refraction.11 min activity

      Try this

      Move the ray or object first, then explain what the diagram is telling you.

      Learn to

      • Use normal lines and ray paths to explain reflection and refraction.
      • Predict when total internal reflection happens by comparing incident angle with critical angle.
      • Relate object position to image nature, size, and orientation for a converging lens.

      Exam transfer

      • Ray diagram
      • Light concepts

      Governing idea

      For a thin converging lens, 1/f = 1/u + 1/v and magnification m = v/u. Reflection obeys i = r, with angles measured from the normal.

      Model boundary

      Ray diagrams use a thin, paraxial lens and selected principal rays. Aberrations, aperture diffraction, and brightness changes are not modeled quantitatively.

      Avoid this trap

      Measure reflection and refraction angles from the normal, not from the surface. A ray diagram locates an image but does not by itself predict its brightness.

      How to explore

      Trace rays through reflection, refraction, TIR, and converging-lens cases in one place.

      Predict the outcome, change one variable at a time, then interpret the result. Completion records participation only and does not award mastery.

      About this activity

      Switch between reflection, refraction, total internal reflection, and converging-lens modes to reason directly from ray diagrams. A text explanation and no-JavaScript route remain available.

      How this activity affects progress
      Course and syllabus information
      Course
      SEC G3 Physics
      Edition
      SEC G3 Physics 2027