The reflected light is completely polarized only when the angle between the reflected and the refracted ray = 90°
POLARIZATION OF LIGHT
2、Selective Absorption
In optical mineralogy we need to produce light which vibrates in a single direction and we need to know the vibration direction of the light ray. The two requirements can be easily met but polarizing the light coming from the light source, by means of a polarizing filter.
2. Wave Normal - a line perpendicular to the wavefront, representing the direction the wave is moving.
3. Light Ray is the direction of propagation of the light energy.
➢Upon entering an anisotropic material, unpolarized light is split into two plane polarized rays whose vibratioin directions are perpendicular to each other, with each ray having about half the total light energy.
=> electromagnetic variations. Wave theory effectively describes the phenomena of polarization, reflection, refraction and interference, which form the basis for optical mineralogy.
This method is used to produce plane polarized light in microscopes, using polarized filters.
Some anisotropic materials have the ability to strongly absorb light vibrating in one direction and transmitting light vibrating at right angles more easily. The ability to selectively transmit and absorb light is termed pleochroism, seen in minerals such as tourmaline, biotite, hornblende, (most amphiboles), some pyroxenes.
§1-1 光学基础概念
二.自然光与偏振光
自然光是在垂直光波传播方向的平面内可以任意方向振动。
直接从光源发出的光均为自然光；自然光经反射、折射或通
过偏光片后成为只在一个固定方向振动的称为平面偏Байду номын сангаас光。
§1-1 光学基础概念 自然光及偏振光
★ POLARIZATION OF LIGHT
Light emanating from some source, sun, or a light bulb, vibrates in all directions at right angles to the direction of propagation and is unpolarized.
§1-1 光学基础概念
The light consists of electric and magnetic components which vibrate at right angles to the direction of propagation. In optical mineralogy only the electric component, referred to as the electric vector, is considered and is referred to as the vibration direction of the light ray.
The behaviour of light within minerals results from the interaction of the electric vector of the light ray with the electric character of the mineral, which is a reflection of the atoms and the chemical bonds within that minerals.
§1-1 光学基础概念
三、光的反射(Reflection)和折射(Refraction)
光线从一种介质射入到另一种时，在两 种介质的分界面上，将产生光的反射和 折射现象，例如水中的筷子的弯曲现象 就是光的折射造成的。
几个概念：传播介质 法线 光疏介质 光密介质
入射光线与入射角 折射光线与折射角
折射率 光在空气（真空）中的传播速度与在晶体中的
Three types of polarization ：Plane Polarization ， Circular Polarization，Elliptical Polarization
POLARIZATION OF LIGHT
In the petrographic microscope plane polarized light is used. For plane polarized light the electric vector of the light ray is allowed to vibrate in a single plane, producing a simple sine wave with a vibration direction lying in the plane of polarization - this is termed plane light or plane polarized light.
was the Nicol Prism. 4、Scattering
Polarization by scattering, not relevant to optical mineralogy, is responsible for the blue colour of the sky and the colours observed at sunset.
➢If anisotropic material is thick enough and strongly pleochroic, one ray is completely absorbed, the other ray passes through the material to emerge and retain its polarization.
一、光的本质
Two complimentary theories have been proposed to explain how light behaves and the form by which it travels.
Particle theory - release of a small amount of energy as a photon when an atom is excited. Wave theory - radiant energy travels as a wave from one point to another. Waves have electrical and magnetic properties
With an infinite number of waves travelling together from a light source, we now define:
1. Wave front - parallel surface connecting similaror equivalent points on adjacent waves.
的传播速度为V=3108m/s = 3105km/s。 电磁波的振动方向与传播方 向相互垂直，故光波亦是横 波。 整个电磁波是一个广阔的区 段。 可见光 单色光与白光
§1-1 光学基础概念
一、光的本质
Light——A form of energy which can be
transmitted from one place to another at finite velocity. Visible light，that which the eye detects, is a small portion of a continuous spectrum of radiation ranging from cosmic rays to radio waves. It is only a fraction of the complete spectrum - produced by shining white light through a glass prism.
二、意义
1、是地质学和无机材料科学的一门专业基础课； 2、是研究物质成分（包括宝石鉴定和材料科学研 究）的重要技术基础课；