Working, Principle and applications of Refractometer

1. An
Overview
on
Refractometer
Prepared by Anil Sharma , Sr. Executive, Compliance,
USV Private Limited
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2. When a ray of light passes
from one medium to another
it suffer refraction.
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3. What is a Refractometer?
A refractometer is a simple instrument used for measuring concentrations of aqueous
solutions. It requires only a few drops of liquid, and is used throughout
the food, agricultural, chemical, and manufacturing industries.
What is Refractive Index?
Refractive Index n is the speed of light in vacuum relative to the speed of light in the
considered medium: n = speed of light in vacuum / speed of light in medium
n = c/v
n = Refractive index.
c = Speed of light in vacuum.
v = Velocity of light in Medium.
Example: Water has a refractive index of 1.33 which means that the light travels 1.33 faster
in vacuum than in water. The refractive index is a physical property of the liquid.
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Snell’s law
Snell's law states that the ratio of the sines of the angles
of incidence and refraction is equivalent to the ratio
of phase velocities in the two media, or equivalent to
the reciprocal of the ratio of the indices of refraction:
θ1 is the angle of Incidence.
θ2 is the angle of Refraction.
V1 is the velocity of light in the Air.
V2 is the velocity of light in the Medium.
N1 Refractive index if Air.
N2 Refractive index if Medium.

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6. How a Refractometer Works
When light enters a liquid it changes direction; this is called refraction.
Refractometers measure the degree to which the light changes direction, called the angle of
refraction. A refractometer takes the refraction angles and correlates them to refractive index
(nD) values that have been established. Using these values, you can determine the
concentrations of solutions.
For example, solutions have different refractive indexes depending on their concentration in
water.
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7. Refraction of light into New Medium:
Light changing speed in a new medium creates a bending.
If light is traveling slower in the new medium i.e. from less dense to more dense medium
like from air to water, it will bend towards the normal line. so that angle of the refraction is
less than angle of incidence.
If light is traveling faster in the new medium i.e. from more dense to less dense medium like
from water to air, it will bend away from the normal line. so that angle of the refraction is
more than angle of incidence.
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Influence of temperature and wavelength
The refractive index depends on the temperature of the media:
The higher the temperature of a media that means the liquid becomes less dense and less
viscous, causing light to travel faster in the medium. Thus higher the speed of light in the
media and the lower its refractive index.
In vacuum light travels at a constant speed (c), independent of its wavelength. In all other
media, however, the speed of light depends as well on its wavelength: The shorter the
wavelength of the light, the higher its speed.
The refractive index has thus always to be stated together with the wavelength of the light
used for the measurement and the temperature of the media.
Its important to use monochromatic lights to prevent dispersion of light into different
colours.
The refractive index is normally measured at a temperature of 20°C using light with the
wavelength of the sodium D line (589.29 nm) and is therefore expressed as nD20.

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Degrees Brix (symbol °Bx) is the sugar content
of an aqueous solution. One degree Brix is 1
gram of sucrose in 100 grams of solution and
represents the strength of the solution
as percentage by mass.
The higher the temperature of a media that
means the liquid becomes less dense and less
viscous, causing light to travel faster in the
medium. Thus higher the speed of light in the
media and the lower its refractive index.

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Uses of Refractive index
 It can be used to characterized liquid and solid samples.
 Measure the concentration of solutions e.g. sugar content in alcohol.
 It can use to check sample for purity.
 RI can be used for qualitative & quantitative analysis as well as structural analysis.
 The refractive index of a substance is dependant on the wavelength λ of the light and
the temperature T of the substance.

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CSV of Refractometer
• URS (J-QC-URS-RFM-01)
 Business Requirements
 Interface Requirements
 Security and safety Requirements
 Electronic Records, Reports and Electronic Signature Requirements
 Audit Trail Requirements
 Backup, Archival and Restoration Requirements
• HLRA (J-QC-HLRA-RFM-01)

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CSV of Refractometer
• IQ (J-QC-IQ-RFM-01)
 Verification of pre-requisite
 Physical Identification
 Verification of system hardware
 Identification of software version
 Environmental Condition Verification
 Verification of Software Backup
 Verification of system startup and shutdown
 Verification of Application installation of Directory
 Date & Time Synchronization Verification
 OPQ (J-QC-OPQ-RFM-01)
 Verification of Draft/Approved SOP
 IQ protocol Completion Verification
 Training Verification, Physical and Logical Security Verification
 User Management Verification, Password Policy Verification
 Verification of Access Control, Verification of Communication Failure