Lab 22 B Polarization of Light 22 B

Lab. 22 B - Polarization of Light 實驗 22 B：光的偏振 I. Object (目的) Observe the polarization phenomena of light. 觀察光的偏振現象 Physics. NTHU MFTai-戴明鳳

Roadmap for Polarization of Light Hyper. Physics http: //hyperphysics. phy-astr. gsu. edu/hbase/hframe. html Physics. NTHU MFTai-戴明鳳

1. Classification of Polarization Light is a transverse (TE) electromagnetic wave (EM wave). Bbut natural light is generally unpolarized, all planes of propagation being equally probable. l Linearly polarized light: in the form of a plane wave in space. l Circularly polarized light: Light is composed of two plane waves of equal amplitude by differing in phase by 90°. l Elliptically polarized light: Two plane waves of differing amplitude are related in phase by 90°, or if the relative phase is other than 90°. l Physics. NTHU MFTai-戴明鳳

1 -1 Linear Polarization (圓偏振) l A plane electromagnetic wave (plane EM wave) is said to be linearly polarized. Physics. NTHU MFTai-戴明鳳

1 -2 Circular Polarization l Circularly polarized light consists of two perpendicular EM plane waves of equal amplitude and 90° difference in phase. Right-Circularly Polarized Light Physics. NTHU MFTai-戴明鳳

Circularly Polarized Light l Light is composed of two plane waves of equal amplitude but differing in phase by 90°. If you could see the tip of the electric field vector, it would appear to be moving in a circle as it approached you. If while looking at the source, the electric vector of the light coming (1)Right-circularly polarized light: toward you appears to be rotating clockwise. (2)Left-circularly polarized light: If counterclockwise. l The electric field vector makes one complete revolution as the light advances one wavelength toward you. l The light may be produced by passing linearly polarized light through a quarter-wave plate at an angle of 45° to the Physics. NTHU optic axis of the plate. MFTai-戴明鳳

Elliptical Polarization Light consists of two perpendicular waves of unequal amplitude which differ in phase by 90°. Physics. NTHU MFTai-戴明鳳

Methods for Achieving Polarization of Light Physics. NTHU MFTai-戴明鳳

Polarization by Reflection Physics. NTHU MFTai-戴明鳳

Reflected Intensity l The reflection coefficients used here are the intensities and not the amplitudes as used in the usual presentation of the Fresnel equations. That is, these reflection coefficients are the square of those in the Fresnel expressions. Physics. NTHU MFTai-戴明鳳

Polarization by Scattering The scattering of light off air molecules produces linearly polarized light in the plane perpendicular to the incident light. l The scatterers can be visualized as tiny antennae which radiate perpendicular to their line of oscillation. If the charges in a molecule are oscillating along the y-axis, it will not radiate along the y-axis. l Therefore, at 90° away from the beam direction, the scattered light is linearly polarized. l This causes the light which undergoes Rayleigh scattering from the blue sky to be partially polarized. l Physics. NTHU MFTai-戴明鳳