# 光

(重新導向自 光線)

## 研究歷史

### 電磁理論

1845年，麥可·法拉第發現當偏振光穿過施加了磁場的透明介質時，會發生偏振旋轉。這後來被稱為法拉第效應，它首次發現了光和電磁的關係。在1846年，他推測光可能是沿磁場線衍生的某種形式的擾動。次年，法拉第提出光是一種高頻電磁振動，不需要介質也能衍生。

## 特性

### 反射

1. 反射線、入射線與法線在同一平面上。
2. 反射線與入射線在法線的兩側。
3. 反射角等於入射角：
${\displaystyle \angle \theta _{i}=\angle \theta _{r}}$

### 折射

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

${\displaystyle v_{2}=v_{1}{\tfrac {\sin \angle \theta _{2}}{\sin \angle \theta _{1}}}}$

${\displaystyle \angle \theta _{2}=90^{\circ }}$ 時，折射光沿著介面運行，這時 ${\displaystyle \angle \theta _{1}}$ 稱為臨界角 ${\displaystyle (\angle \theta _{c})}$；當 ${\displaystyle \angle \theta _{1}>\angle \theta _{c}}$ 時，入射光則完全反射回原介質，稱為全內反射。

## 參考文獻

1. ^ International Commission on Illumination (1987). International Lighting Vocabulary 網際網路檔案館存檔，存檔日期2010-02-27.. Number 17.4. CIE, 4th edition. ISBN 978-3-900734-07-7.
By the International Lighting Vocabulary, the definition of light is: 「Any radiation capable of causing a visual sensation directly.」
2. ^ Pal, G. K.; Pal, Pravati. chapter 52. Textbook of Practical Physiology 1st. Chennai: Orient Blackswan. 2001: 387 [11 October 2013]. ISBN 978-81-250-2021-9. The human eye has the ability to respond to all the wavelengths of light from 400-700 nm. This is called the visible part of the spectrum.
3. ^ Buser, Pierre A.; Imbert, Michel. Vision. MIT Press. 1992: 50 [11 October 2013]. ISBN 978-0-262-02336-8. Light is a special class of radiant energy embracing wavelengths between 400 and 700 nm (or mμ), or 4000 to 7000 Å.
4. ^ Laufer, Gabriel. Introduction to Optics and Lasers in Engineering. Cambridge University Press. 13 July 1996: 11 [20 October 2013]. ISBN 978-0-521-45233-5.
5. ^ Bradt, Hale. Astronomy Methods: A Physical Approach to Astronomical Observations. Cambridge University Press. 2004: 26 [20 October 2013]. ISBN 978-0-521-53551-9.
6. ^ Ohannesian, Lena; Streeter, Anthony. Handbook of Pharmaceutical Analysis. CRC Press. 9 November 2001: 187 [20 October 2013]. ISBN 978-0-8247-4194-5.
7. ^ Ahluwalia, V. K.; Goyal, Madhuri. A Textbook of Organic Chemistry. Narosa. 1 January 2000: 110 [20 October 2013]. ISBN 978-81-7319-159-6.
8. ^ 各個波段的電磁波特徵與用途
9. ^ 近紅外光譜儀
10. ^ X光對人體的影響
11. ^ Whittaker, E. T., A history of the theories of aether and electricity. Vol 1, Nelson, London, 1951
12. ^ Hecht, Eugene, Optics 4th, United States of America: Addison Wesley: pp. 106–111, 141, 2002, ISBN 0-8053-8566-5 （英語）
13. ^