can a refractive index be less than 1
Refractive index According to the theory of relativity, no information can travel faster than the speed of light in vacuum, but this does not mean that the refractive index cannot be lower than 1. The refractive index measures the phase velocity of light, which does not carry information.[19] The phase velocity is the speed at which the crests of the wave move and can be faster than the speed of light in vacuum, and thereby give a refractive index below 1. This can occur close to resonance frequencies, for absorbing media, in plasmas, and for X-rays. In the X-ray regime the refractive indices are lower than but very close to 1 (exceptions close to some resonance frequencies).[20] As an example, water has a refractive index of 6999999999740000000♠0.99999974 = 1 − 6993260000000000000♠2.6×10−7 for X-ray radiation at a photon energy of 6985480652946099999♠30 keV (0.04 nm wavelength).[20]
Color Electromagnetic radiation is characterized by its wavelength (or frequency) and its intensity. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 390 nm to 700 nm), it is known as "visible light".
Exponentiation Any nonzero number raised to the 0 power is 1:[11]
Dividend yield Its reciprocal is the Price/Dividend ratio.