Refractive index database

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Optical constants of Air
Mathar 2007: n 4.35–5.2 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants

Conditions & Spec sheet

n_is_absolute: true
wavelength_is_vacuum: true
temperature: 15 °C
pressure: 101325 Pa


Dry air at 15 °C, 101.325 kPa, 370 ppm CO2 content.


R. J. Mathar. Refractive index of humid air in the infrared: model fits, J. Opt. A: Pure Appl. Opt. 9, 470-476 (2007)
[Calculation script (Python) - can be used to calculate the refractive index of air for specific values of humidity, temperature, and pressure]


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Air is a mixture of gases that constitutes the Earth's atmosphere and is vital for most forms of life on our planet. It primarily consists of nitrogen (approximately 78%) and oxygen (about 21%), with small amounts of other gases such as argon, carbon dioxide, neon, helium, and methane. The exact composition can vary depending on location and environmental conditions. Air is colorless, odorless, and tasteless. From a physical perspective, air plays a crucial role in many processes such as weather patterns, the water cycle, and is also an important medium for sound transmission. In terms of its optical properties, air has a refractive index very close to 1 (approximately 1.0003 at sea level under standard conditions), which varies slightly with temperature, humidity, and pressure. This refractive index is crucial in various applications ranging from astronomical observations to the design of optical systems where light travels through the atmosphere. Understanding the properties of air, including its refractive index, is essential for disciplines such as meteorology, environmental science, aviation, and optical engineering.

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