1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

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Transcript of 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

  • *Polarization*

  • PolarisationXY Plane: Plane of polarisation

  • S =(E x B)/o

  • Unpolarized lightPolaroid: Transmits along the pass axis and absorbs along the perpendicular axis

  • Malus law

  • Unpolarized light

  • Degree of polarisationIf the incident light is a mixture of unpolarised light of intensity Iuand polarised light of intensity Ip, then the transmitted light is given by:

  • Polarisation by scattering

  • Rayleigh scatteringBlue skyRed Sunset / Sunrise

  • Convention

  • - PolarisationPlane of polarisation is same as plane of incidence- PolarisationPlane of polarisation is perpendicular to the plane of incidence

  • Polarisation by reflection

  • Brewster angleGlasspartially polarisedlinearly polarisedunpolarised polarised

  • Brewster angle

  • = Brewster angleBrewsters law

  • Polarisation by reflection

  • Polarisation by double refraction- Two refracted beams emerge instead of one- Two images instead of oneCalciteQuartzOptic Axis: Uniaxial crystals exhibit cylindrical symmetry. There is a unique direction in a uniaxial crystal called the optic axis.Values of physical parameters along optic axis are different from the values perpendicular to it.

  • CalciteExtraordinary rayOrdinary rayOptic axisPrincipalPlane:Plane contains optic axis and the direction of propagation

  • CalcitePolariser/AnalyserOrdinary ray - polarised

  • Extraordinary ray - polarised Calcite

  • Polarisation by double refractionIsotropic Medium : Velocity Spherical

  • - PolarisationPlane of polarisation is same as plane of incidence (principal plane)- PolarisationPlane of polarisation is perpendicular to the plane of incidence (principal plane)Plane of incidence : plane contains incident ray, reflected/refracted ray, surface normalPlane of polarisation : plane contains electric field vector and direction of propagation Principal plane : Plane contains optic axis and the direction of propagationThis definitionis considered in absence of Principal Plane

  • e-ray : Plane of polarisation is same as principal plane Plane of polarisation is perpendicular to the principal plane o-ray : e-ray in general does not obey the laws of refraction except in case of special cut of crystal (optic axis) o-ray always obeys the laws of refraction Always e-ray carries -polarisation and o-ray carries -polarisation

  • Positive and Negative uniaxial crystalsQuartz - Positive (ne - no)>0Calcite - Negative (ne - no) nove < voVelocity or Refractive index is the same along the OPTIC AXIS for o-ray and e-ray.ne < nove > vo

  • QuartzPositive crystalSphereSpheroidWave surface is the locus of all points reached by the ray at a given instantVelocity ellipsoidne > nove < vo

  • SphereSpheroidne > nove < voQuartzPositive crystal

  • SphereSpheroidne > nove < voQuartzPositive crystal

  • CalciteNegative crystalSphereSpheroidne < nove > vo

  • SphereSpheroidne < nove > voCalciteNegative crystal

  • SphereSpheroidne < nove > voCalciteNegative crystal

  • Biaxial

  • Huygensconstruction

  • Calcitene < nove > vo

  • Special cuts of uniaxial crystalOptic axis normal to the surface of incidenceNo double refraction

  • Optic axis parallel to the surface of incidenceNo double refraction

  • Oblique IncidenceOptic axis parallel to the surface of incidence, normal to the plane of incidence

  • Nicol prismCalciteCanada balsamn = 1.55no = 1.6584ne = 1.4864

  • Rochon prism

  • Wollaston prism

  • Elliptical and circular polarisationPlane polarisedCircularly polarisedEtc.

  • Production of elliptically polarised lightOEAO =E =

  • RetardersQuarter wave, Half wave and Full wave

  • GLASS

  • Quartz

  • QuartzHalf wave plate

  • Variable retarderBabinet Compensatoris a. . . . . . . . . . . . . . . . . . . .. . . . . . . . .C

  • Interference of polarised lightFresnel-Arago lawsTwo coherent rays polarised at right angles do not interfere2. Two parallel coherent polarised rays will interfere in the same way as will ordinary light

  • Optically active mediumSpecific rotation= 21.72 Deg/mmfor Sodium linesRotation of the plane of vibration & Rotatary dispersionDextrorotatary or right handed mediumLevorotatary or left handed medium

  • Sugar, Glucose and FructoseSugar (Sucrose or Cane sugar) Glucose-D ( Dextrose or Grape sugar)Fructose (Levulose or Fruit sugar)Specific rotation52.766.47- 92ooo

  • Specific rotation is defined as the observed rotation of light of wavelength 589 nm (the d line of a sodium lamp) passing through 10 cm of a 1 g ml-1 solution of a sample. Rotation in liquidsOne can find out the density of substance in solution[] = 10 / ldSpecific rotation, = angle of rotationl = Length of the liquid column in cmd = density in gm/cm3

  • Fresnels explanation of rotation

  • Induced Optical EffectsIsotropic medium can be made optically anisotropic applyingStress : Photoelastic EffectMagnetic field : Faraday EffectElectric field : Kerr effect

  • Faraday effectBd=Verdet cosntant0.00001-0.01 min/Gauss-cm

  • Kerr effectAn isotropic medium becomes birefringent by an application of electric field.

    It behaves like an uniaxial crystal with optic axis in the direction of applied field.K = Kerr Constant

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