Measure from the normal
Angles use the dotted line perpendicular to the surface, rather than the surface itself.
Bending Light Lab
Trace refracted rays, explore total internal reflection and compare apparent depth.
Grades 3–5 · Physics
Your goal
From air into water, set the incident angle to 20° and inspect the bent ray.
Reduced motion is on. The controls still update the scene.
Incident 0° and refracted 0.0°, measured from the normal. Index changes from 1.00 to 1.33. The near-normal apparent depth is 45.0 cm.
degrees
cm
The left picture obeys Snell's law for one flat boundary. The right picture is a separate viewing example with an observer in the upper medium. Its apparent depth uses the near-normal approximation and does not trace the angled ray on the left. Air index is 1, water is 4/3 and glass is 1.5. Surface waves, dispersion and reflected brightness are omitted.
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Learn with Bending Light Lab
Bending Light Lab introduces elementary learners to the way light changes direction at a boundary. Choose air to water, water to air or glass to air, then adjust the incident angle measured from the dotted normal. Compare the transmitted ray with the reflected ray and find settings that produce total internal reflection. A separate object-depth control shows why a submerged object can appear closer to a surface when viewed almost straight down. Guided goals distinguish exact ray geometry from the simpler apparent-depth approximation shown alongside it.
What to look for
Try a critical angle
Send light from water or glass into air and increase the angle to find total internal reflection.
Compare two diagrams
The separate depth picture uses a near-normal viewing approximation rather than the angled ray trace.
For teachers and curious learners
Explore how refractive index changes ray direction and apparent object depth. Ask students to predict what will happen, change one setting, and explain what they observe. Learn gives a starting point. Practice and Challenge offer new goals with the same scene.
Snell geometry uses air index 1, water 4/3 and glass 1.5. Total internal reflection occurs only beyond the higher-to-lower critical angle. Apparent depth is a separate near-normal approximation; dispersion and reflected brightness are omitted.