Download Polarized light is generated by the standard (unpolarized) light

Polarized light is generated by the standard (unpolarized) light through an
optical prism – nikol. The result is a light whose rays oscillate in one plane only.
If passing polarized light through a solution containing an optically active
substance (a substance that contains in its molecule, asymmetrical carbon), the
rotation of the plane of polarized light occurs (to be given in degrees α). This
rate of rotation depends directly and proportionally on the properties of a
particular active substance, concentration, the strength of layers, in proportion
to the wave length of light and temperature. The rotation angle of the plane
polarized light is measured by Polarimeter. Polarimetric measurements we use
in analytical chemistry to the qualitative and quantitative determination of the
optically active substances.
Dependence of angle rotation plane of the polarized light from the content of
the analyte in the environment reflects the Biotov formula: α = [α]λt . d . w
Where: [α]ϒt - the specific rotation of a substance which is a characteristic
constant for each substance at a temperature of ta wavelength λ (v ° . dm3 . g -1
. m-1) d - is the thickness of the layer environment (in meters) and a w is the
mass concentration of the analyte (v g.dm-3).
The rotation of the plane of polarized light depends on: – the nature of the
substance (structure)
• the concentration of
• other factors ( from the length of the light passes through the layers)
Oscillation of the electromagnetic field of the beam of light is done randomly
on the plain in all planes perpendicular to its direction. If the influence of
vibrations of a particular environment takes place in only one plane, called a
constant plane, we're talking about polarized light.
Plane perpendicular to the plane of the oscillating is called a polarized plane
(plane polarized light).Light can be a reflection of the simplest polarization,
however, double break.
Double greak occurs when passing light through the crystals of all systems, in
addition to the cubest. If double break crystal passes through the ray light
beam in a direction that is not identical with the direction of the optical axis
(parallel to the axis of the optical axis direction = crystalgraphic), spina at the
two polarized rays with the same intensity.
These rays are taking off in the crystal and stand out from him in a direction
parallel to the initial direction. Both rays are oscillate in mutually perpendicular
planes. The real beam r oscillates in the plane perpendicular to the plane of the
impact of the extraordinary ray m v in the plane of the impact.
The best double breaking crystal is Iceland's limestone. The refractive index of
the extraordinary beam is less than the index of the real beam.
This property is used in the construction of polarizing prisms. The frontal area
of the edges are sharpen off, so that they clench an angle of 68 ° , they will be
perpendicularly cut apart to the frontal surface area creating nikol which
surfaces are polished and glueted together with Canadian balsam. This
adjustment allows you to make an extraordinary beam passed through entire
prism, while real beam falls on the balsam layer under a larger angle than the
cutoff angle and is entirelly reflected.
If we´re releasing a monochromatic light through two nikols fastened in one
axis, depending on the illumination of the visual field from their mutual
position. The first nikol is called the polarizer (P), the second nikol, which
transmitted light we observe is Analyzer.If they are both in parallel, the visual
field is totally clear. If we´re rotating analyser around it´s common axis, the
field gradually darkens.When rotate by 90 ° are nikols in crossed position and
visual field is completelly dark. With the next turn, visual field is getting
brighter, at an angle of 180 ° it is completely bright. The intensity of the visual
field by analogy is changing with every next turn from an angle of 180 ° to 360
°. If we insert the quartz plate between crossed nikols which walls are
perpendicular to the optical axis of the crystal, the visual field is getts bright.
If we would like to reach a darkness again, it is necessary to rotate the analyzer
about a certain angle, which we call the rotation angle of the plane polarized
light. If the nikols are in the parallel position, the quartz plate causes a darkness
of the visual field and for brightness, we need to rotate the analyzer about the
same angle. We say, that the quartz plate is optically active and that rotates the
plane of polarized light.