# Electrical Measurement and Instrumentation

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Electrical Measurement and Instrumentation
Refractive index measurement is actually a measurement of the speed of light in a medium. The speed of light (usually denoted by c) is 299 792 458 m/s in vacuum. In other media the speed of light is lower than this value, and the refractive index, R.I., of a medium is a measure of how much the speed of light is reduced in the medium. The refractive index (n) of a medium is defined as the ratio of speed of light in vacuum (c) in to that in the medium (v)
The speed of light in a medium depends on the medium itself, temperature and wavelength. Due to the wavelength dependency, the refractive index is measured with monochromatic light. The refractive index is commonly determined as part of the characterization of liquid samples, in much the same way that melting points are routinely obtained to characterize solid compounds. It is also commonly used to: * Help identify or confirm the identity of a sample by comparing its refractive index to known values. * Assess the purity of a sample by comparing its refractive index to the value for the pure substance. * Determine the concentration of a solute in a solution by comparing the solution's refractive index to a standard curve.
To know about refractive index measurement first of all we know something about refractive index.

What is refractive index?
In optics the refractive index or index of refraction n of a substance (optical medium) is a dimensionless number that describes how light, or any other radiation, propagates through that medium. It is defined as
,
Where, where c is the speed of light in vacuum v is the speed of light in the substance example, the refractive index of water is 1.33, meaning that light travels 1.33 times as fast in vacuum as it does in water
The historically first occurrence of the refractive index was in Snell's law of refraction, n1sinθ1= n2sinθ2, where θ1 and θ2 are the angles of incidence of a ray crossing the interface between two media with refractive indicesn1

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