Bend a little light
Refraction & total internal reflection
Change the incident angle and refractive indices to see a ray bend or reflect internally.
Refraction & total internal reflectionTRY IT YOURSELF
Refracted angle22.48°
Critical angleNot applicable
Incident angle35 °
BehaviorTransmission
Teal + amber · follow the changing valuesIdealized physics model
What if you changed…
Try a starting point
Travel from glass to air. Find the angle where the refracted ray disappears.
See the calculation
n₁ sin θ₁ = n₂ sin θ₂
- sin θ₂ = n₁ sin θ₁ / n₂ = 0.3824.
- θ₂ = arcsin(0.3824) = 22.48° from the normal.
- Total internal reflection is not possible in this direction.
What this model assumes
Flat interface between transparent media. Angles are measured from the normal; ray intensity and partial reflection are not modeled.
Keep an eye on this
Always measure the ray angle from the normal to the boundary, not from the boundary itself.
Understand the physics ↗A little question. A clearer picture.
Refraction & total internal reflection: common questions
Wondering about the why? Start here.
When does total internal reflection occur?
When n₁ > n₂ and the incident angle exceeds arcsin(n₂/n₁). At the critical angle, the refracted ray travels along the boundary.
Does light always bend at a boundary?
At normal incidence, its direction stays the same. There is also no directional change if both media have the same refractive index.