Snell's Law Calculator

Yes -- because the equation solves sin(θ₂) = n₁ sin(θ₁) / n₂, and n₂ sits alone in the denominator, raising it always pulls sin(θ₂) down and bends the ray closer to the surface normal, regardless of what the incident angle or n₁ happen to be. Refractive Index n₁ and the Incident Angle move the result the opposite way: raising either one always increases the refraction angle instead.

That happens when n₁ sin(θ₁) / n₂ works out to a value greater than 1, which is only possible when light travels from a higher-index medium into a lower-index one (n₁ greater than n₂) at an incident angle beyond the Critical Angle. Past that angle, no refracted ray exists -- all the light reflects back into the first medium, which is how fiber-optic cables and prism binoculars work.

The Critical Angle is the incident angle at which the refraction angle reaches exactly 90°, calculated as the arcsine of n₂ divided by n₁. It only exists when n₁ is greater than n₂; if the first medium is less dense than the second, the calculator reports "N/A" because a ray moving into a denser medium can never hit total internal reflection, at any incident angle.

No -- Reflectance and Transmittance always add up to 1 (or 100%): whatever fraction of light intensity is not reflected at the interface is transmitted into the second medium instead. A Reflectance of 0.04, for example, means about 4% of the light bounces back and about 96% continues on as the refracted ray, with no light actually lost from the system.

Real materials have a refractive index that varies slightly with wavelength -- a property called dispersion, and the reason a prism splits white light into a rainbow. This calculator takes n₁ and n₂ as single fixed values, so it models one wavelength at a time; to see the spread of colors you would need to run it once per wavelength using that material's dispersion curve.