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• 광학의 기본 지식

• 빛이란 무엇인가?

• 파동인가 입자인가?

• 광학은 전자기학과 어떤 관계인가?

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빛의 3가지 모형

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Charge free space or no source : vacuum or r=0

o

E H

 ^ t

  



o

H E

 ^ t

 



0

   E

0

  H 





: 전기마당 근원이 0임

: 자기마당 근원이 0임

Maxwell’s equation

빛의 전파

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고체내부의 편광

Wave equations in vacuum

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2 2

2 2

1 E 0 E c t

   



2 2

2 2

1 H 0 H c t

   



전기마당이나 자기마당의 파동방정식이 동일한 형태임.

진공 속에서 광속(c)은 상수로 결정됨.

1

3 10 / sec

o o

c m

    

Speed of light in a medium

1 1

o r o r r r

c c

u c

       n

    

상대적 전기유전률과 상대적 자기투자율

r

1

o

 

  

1

o

 

  

n 은 파동이 통과하는 매질의 굴절률이다.

r r

1

n    

보통물질의 굴절률

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빛이 통과하는 보통의 비자기적 물질은 상대적 자기투자율이 1 이다. 따라서 전기유전률이 굴절률을 결정한다.

n  

광속 측정의 역사

• The speed of light in a vacuum is defined to be exactly 299,792,458 m/s. The fixed value of the speed of light in SI units results from the fact that the meter is now

defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum.

• Different physicists have attempted to measure the speed of light throughout history. Galileo attempted to measure the speed of light in the seventeenth century.

• An early experiment to measure the speed of light was conducted by Ole Rømer, a Danish physicist, in 1676.

Using a telescope, he observed the motions of Jupiter and one of its moons, Io.

• Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about 22 minutes to

traverse the diameter of Earth's orbit. However, its size was not known at that time.

• If he had known the diameter of the Earth's orbit, he would have calculated a speed of 227,000,000 m/s.

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• In 1849, Fizeau directed a beam of light at a mirror several kilometers away. A rotating cog wheel was

placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its origin.

• Fizeau found that at a certain rate of rotation, the beam would pass through one gap in the wheel on the way out and the next gap on the way back.

• Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau was able to calculate the speed of light as 313,000,000 m/s.

• Léon Foucault used an experiment which used rotating mirrors to obtain a value of 298,000,000 m/s in 1862.

• Albert A. Michelson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mount Wilson to Mount San

Antonio in California. The precise measurements yielded a speed of 299,796,000 m/s.

• The effective velocity of light in various transparent substances containing ordinary matter, is less than in vacuum. For example the speed of light in water is about 3/4 of that in vacuum.

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