Glass to Air: Near Critical Angle (41°)
Light travelling from glass (n=1.5) to air at 41° refracts close to 90°, near the critical angle for total internal reflection.
How to use this tool
- Enter refractive index n₁, angle of incidence θ₁ and refractive index n₂ in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your angle of refraction θ₂ and the full breakdown beneath it.
The critical angle for glass-to-air is about 41.8°; this preset shows refraction just below that threshold.
Frequently asked questions
- What is total internal reflection?
- When light in a denser medium (e.g. glass) hits the boundary at an angle greater than the critical angle, all light is reflected back. This is the principle behind fibre-optic cables.
- What are common refractive indices?
- Vacuum/air: 1.0, water: 1.33, crown glass: 1.52, diamond: 2.42.