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What is Light?What is Light?Wave or Particle?

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What is Light?What is Light?Early Accounts:Early Accounts:

Pythagoras (ca. 582-500 B.C.), Greek philosopher- Stream of particles emitte from a! o"#ect

Aristotle (38 !3"" #$%$&' ree) philosopher! *oved as a +ave' li)e ripples on +ater

Wave

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What is Light?What is Light?,-,- thth!!,8,8 thth %entury%entury

.saac Ne+ton (,/ " 0,-"-& English physicist'1athe1atician' astrono1er' naturalphilosopher' alche1ist' and theologian

- Hypothesis of Light ($%&5), light iscompose of corp'scles (particles of matter)

hich ere emitte i! all irectio!s from aso'rce.

- a*es ere k!o ! to "e! aro'!o"stacles, hile light tra*elle o!ly i! straightli!es.

Particle

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What is Light?What is Light?

,-,- thth!!,8,8 thth %entury%entury2ho1as oung (,--3!,8"4&' English physician and physicist

! studied diffraction and

,853! opposed to the particleor corpuscular theory of

.saac Ne+ton

Wave

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What is Light?What is Light?

,4,4 thth!!"5"5 thth %entury%entury

6a1es *a7+ell (,83,!,8-4&' English Physicist

!electro1agnetic +ave' ustli)e radio +ave' 7!ray and1icro+aves

! Light follo+s +avee9uation

Wave

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What is Light?What is Light?,4,4 thth!!"5"5 thth %entury%entury

Al ert Einstein (,8-4!,4;;&' er1an! orntheoretical physicist

Particle

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What is Light?What is Light?! Photoelectric effect' light energy is 9uanti

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What is Light?What is Light?

Particle- a*e +'alitya*e Particle

!terfere!ce+iffractio!

a*e e/'atio!

i!ear patheflectio!efractio!

1'a!ti e

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What is Light?What is Light?

! A for1 of energy that is visi le to thehu1an eye' sometimes displays properties

o +aves an some mes sp aysproperties of particles$

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Speed of lightSpeed of light3la's 4mer ($% -$&$0), +a!ish physicist

- 6irst /'a!titati*e estimate of the spee of light,ma e i! $%&% - 3"ser*e that the perio s of 7'piter s i!!ermostmoo! o appeare to "e shorter he! the 9arth asapproachi!g 7'piter tha! he! rece i!g from it, he

co!cl' e that light tra*els at a fi!ite spee , a!estimate that it takes light 22 mi!'tes to cross the

iameter of 9arth s or"it.

- 2.$ : $0 8 m;s

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Speed of lightSpeed of light%hristiaan =uygens (,/"4 0,/4;&'>utch 1athe1atician' astrono1er' and physicist

! co1 ined the esti1ate of @1er +ith an esti1ate

for the dia1eter of the Earth s or it! "$"5 7 ,5 8 1Bs

*ore accurateC

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Speed of lightSpeed of lightAl ert *ichelson (,8;"!,43,&' er1an! ornA1erican physicist

! Dsed 1irrors 3; )1 a+ay

! $ $ 7 1 s! "44'-4"' ;/$" ,$, 1Bs

*uch 1ore accurateC

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Speed of lightSpeed of light$5th Co!f