Index of refraction of any material is strongly dependent on the wavelength (frequency) of light used to measure it. Standard index of refraction measurements are taken at the "yellow doublet" sodium D line, with a wavelength of 589 nanometers (509 THz).

Material	Index of Refraction	State
Vacuum	1		(by definition)
Helium	1.000036	Gas	(0°C and 1 atm)
Hydrogen	1.000132	Gas	(0°C and 1 atm)
Air	1.000277	Gas	(at STP*)
Air	1.000293	Gas	(0°C and 1 atm)
Carbon Dioxide	1.001	Gas	(0°C and 1 atm)
Liquid Helium	1.025	Liquid	(at -270°C)
Water Ice	1.31	Solid	(at 0°C)
Water	1.330	Liquid	(at 20°C)
Acetone	1.36	Liquid	(at 20°C)
Ethanol	1.361	Liquid	(at 20°C)
Kerosene	1.39	Liquid	(at 20°C)
Corn Oil	1.47	Liquid	(at 20°C)
Glycerol	1.4729	Liquid	(at 20°C)
Acrylic Glass	1.490–1.492	Solid	(at 20°C)
Benzene	1.501	Liquid	(at 20°C)
Crown Glass (pure)	1.50–1.54	Solid	(at 20°C)
Plate Glass (window glass)	1.52	Solid	(at 20°C)
Sodium Chloride (table salt)	1.544	Solid	(at 20°C)
Amber	1.55	Solid	(at 20°C)
Polycabonate	1.60	Solid	(at 20°C)
Flint Glass (pure)	1.60–1.62	Solid	(at 20°C)
Bromine	1.661	Liquid	(at 20°C)
Sapphire	1.762–1.778	Solid	(at 20°C)
Cubic Zirconia	2.15–2.18	Solid	(at 20°C)
Diamond	2.417	Solid	(at 20°C)
Silicon	3.42–3.48	Solid	(at 20°C)
Germanium	4.05–4.01	Solid	(at 20°C)

*STP is defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 105 Pa (100 kPa, 1 bar).