# 光學

• 幾何光學會用到幾何學上嘅概念，分析光點樣喺空間當中行進；幾何光學會將光當成射線噉嚟睇，即係將光當成係以完美直線嘅軌道前進嘅數學物體，靠噉嚟分析反射同埋折射等嘅現象，並且再研究呢啲現象會點樣解釋到喺等嘅架生上面出現嘅影像[3]；例如好出名嘅折射定律就可以用類似以下噉嘅方程式嚟總括，表述 ${\displaystyle \theta _{1}}$${\displaystyle \theta _{2}}$（簡單講就係光射線條軌跡成嘅某啲角度）間有乜嘢啦掕[4] ——
${\displaystyle n_{1}\sin \theta _{1}=n_{2}\sin \theta _{2}\ }$
• 物理光學就主要研究光呢樣嘢本身嘅性質，例子可以睇吓光子等嘅概念；物理光學亦都會研究幾何光學嗰種「將光睇成射線」嘅分析方法搞唔掂嘅現象，好似係干涉繞射呀噉[5]

## 幾何光學

... 呀噉[12]。幾何光學係好早期嘅光學研究框架－早喺公元 984 年嗰時經已有中東嘅學者喺度講反射定律嘅嘢[13]

### 反射

${\displaystyle \theta _{r}=\theta _{i}}$

### 折射

${\displaystyle {\frac {\sin \theta _{1}}{\sin \theta _{2}}}={\frac {v_{1}}{v_{2}}}={\frac {n_{2}}{n_{1}}}}$

${\displaystyle n_{1}\sin \theta _{1}=n_{2}\sin \theta _{2}\ }$

## 註釋

1. 講緊以古典物理學對物質嘅認識嚟講。詳情可以睇量子力學方面嘅內容。
2. 呢啲特性只係幾何光學為咗方便分析而做嘅概念簡化。
3. 即係話幾何光學高度抽象化，忽視咗光嘅種種波動特性。

## 參考

1. EM waves
2. geometric optics
3. reflection
4. law of reflection
5. normal；指同塊鏡嘅表面成垂直嘅線
6. refraction
7. law of refraction / Snell's law
8. chromatic aberration
9. lens，大致似粵拼 len1 si2
10. concave lens
11. convex lens
12. diverging lens
13. focal point
14. converging lens
15. focal length
16. physical optics
17. visible light
18. superposition principle
19. constructive interference
20. destructive interference
21. diffraction
22. polarization
23. polarized

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