Light and its propagation
1. Nature of light
Particle or wave?
- 1700 Praticle theory;
- 1800 Wave theory, interference & diffraction;
- 1900 Particle: photon, Wave-particle daulity, Quantum electronynamics, QED.
关于光:视觉,直线传播,反射定律
光传播需要时间么?光行差.
1.1. "What is light?"
1.1.1. 微粒模型
直线传播+光可在真空中传播
Particle theory of light; Corpuscular theory of light.
1.1.2. Wave theories of light
Christian Huygens(1629-1695) Each point on the existing wave-front can be considered to act as source of waves (sometimes referred to as "secondary wavelets").
What kind of wave? Maxwell: light is an electromagnetic wave!
Experimental support: Heinrich Hertz
1.1.3. 辐射的粒子特性
1897, JJ Thomson 发现电子,两年后发现光照射到金属表面会有电子跑出
关键实验:1902 年,Philip Lenard, 光电效应
- 光电子动能与光强无关;
- 与照射光的频率有正相关.
爱因斯坦:光量子,动量
2. Light source and spectrum
2.1. Light soources
- Thermal radiation: electromagnetic radiaton emitted form the surface of an object which is due to the object`s temperature.
- Non-thermal radiation
- Electroluminescence 电致发光
- An optical phenomenna and electical phenomenon in which a material emtis light in respnse to an electric current passed through it.
- Photoluminescence 光致发光
- Fluorescence
- Phosphorescence
- Chemiluminescence
- Bio-luminescence.
2.2. Spectrum
- Electromagnetic spectrum
- Visible spectrum.