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Aequationes Fresnel: Quid sunt? (Derivatio et Explicatio)

Electrical4u
Campus: Electrica Elementaria
0
China

Quid sunt Aequationes Fresnel?

Aequationes Fresnel (etiam cognitae ut coefficientes Fresnel) definuntur ut ratio campi electrici undae reflectae et transmissae ad campum electricum undae incidentis. Haec ratio est complexa, et ideo describit amplitudinem relativam tamquam et mutationes phase inter undas.

Aequationes Fresnel (coefficientes Fresnel) describunt reflectionem et transmissionem lucis quando incidentia est in interficiem inter duos diversos media. Aequationes Fresnel introductae sunt ab Augustin-Jean Fresnel. Ille fuit primus qui intellexit lucem esse undam transversalem.

Cum lux incidentia est in superficiem dielectrici, reflectetur et refringetur secundum angulum incidentiae. Directio undae reflectae datur per "Legem Reflectionis".

Effectus Fresnel videtur in vita regulari. Videtur in superficiebus nitidis et asperis. Hic effectus clare apparet in superficie aquae. Cum lux incidentia est in aquam ex medio aeris, lux reflectetur secundum angulum incidentiae.

Effectus Fresnel ubique est. Si conaris circumspicere, multos exemplorum invenies. Hic effectus valde dependet ab angulo incidentiae.

Angulus incidentiae est angulus inter lineam visus et superficiem objecti quod spectas. Figura infra ostendit effectum anguli incidentiae in reflectione Fresnel.

Polarizationes S et P

Planum quod habet normalem superficiei et vectorem propagationis radiationis incidentis vocatur planum incidentiae vel planum incidentis.

Planum incidentiae iocari potest partem magnam in fortitudine reflectionis polarizationis lucis incidentis. Polarizatio definitur ut proprietas undae transversalis quae specificat orientationem geometricam oscillationis.

Sunt duo genera polarizationis;

  • Polarizatio S

  • Polarizatio P

Cum polarizatio lucis sit perpendicularis ad planum incidentiae, polarizatio dicitur S-polarizatio. Verbum 'S' derivatur a verbo Germanico senkrecht quod significat perpendicularis. S-polarizatio etiam cognoscitur ut Electricum Transversale (TE).

Cum polarizatio lucis est parallela plano incidentiae vel in illo plano iacet. Id planum P-Polarization dicitur. S-polarization etiam Transverse Magnetic (TM) dicitur.

Figura infra monstrat lumen incidentem reflexum et transmissum in S-polarization et P-Polarization.

Aequationes Fresnel Complexus Index Refractionis

Aequationes Fresnel sunt aequationes complexae, quae magnitudinem et phasem simul considerant. Aequationes Fresnel repraesentant amplitudinem complexam campi electromagneticum, quae phasem praeter potentiam considerat.

Hae aequationes sunt rationes campi electromagneticum et in varias formas fiunt. Coefficientes amplitudinis complexae per r et t designantur.

Coefficient reflectivus 'r' est ratio amplitudinis complexae campi electrici undae reflexae ad undam incidentem. Coefficient transmissivus 't' est ratio amplitudinis complexae campi electrici undae transmissae ad undam incidentem.

Ut in figura supra ostenditur, angulum incidentiae θi assumimus, reflexum ad angulum θr, et transmissum ad angulum θt.

Ni sunt indices refractionis medii luminis incidentis et Nt sunt indices refractionis medii luminis transmissi.

Ita, quatuor aequationes Fresnel sunt; duae aequationes pro coefficiente reflectionis 'r' (rp et rs) et duae aequationes pro coefficiente transmissionis 't' (tp et ts).

Aequationes Fresnel Derivatio

Assumamus lumen incidentem sicut in figura supra ostenditur. In primo casu, derivabimus aequationem Fresnel pro S-Polarization.

Pro S-Polarization, componentes parallelus E et perpendicularis B sunt continui inter fines duorum mediorum.

Ex conditione termini, possumus aequationes scribere pro campo E et campo B,

(1) \begin{equation*}E_i + E_r = E_t\end{equation*}


\begin{equation*}B_i \cos(\theta_i) - B_r \cos(\theta_r) = B_t \cos(\theta_t)\end{equation*}

Utamus relatione infra inter B et E ad eliminandum B. 

\[ B = \frac{nE}{c_0} \]

Et ex lege reflexionis, 

\[ \theta_i = \theta_r \]


Pone hanc valorem in eq-2,

(3) 

\begin{equation*} \frac{n_i E_i}{c_0} \cos(\theta_i) - \frac{n_i E_r}{c_0} \cos(\theta_i)  = \frac{n_t E_t}{c_0} \cos(\theta_t)  \end{equation*}


(IV) 

\begin{equation*}n_i \cos(\theta_i) [ E_i - E_r ] = n_t E_t \cos(\theta_t)  \end{equation*}


(V) 

\begin{equation*}n_i \cos(\theta_i) [ E_i - E_r ] = n_t [ E_i + E_r ] \cos(\theta_t)  \end{equation*}


(VI) 

\begin{equation*}n_i E_i \cos(\theta_i) - n_i E_r \cos(\theta_i) = n_t E_i \cos(\theta_t) + n_t E_r \cos(\theta_t)\end{equation*}


(VII) 

\begin{equation*}n_i E_i \cos(\theta_i) -  n_t E_i \cos(\theta_t) =  n_t E_r \cos(\theta_t) +  n_i E_r \cos(\theta_i) \end{equation*}


(8)
 

\begin{equation*}E_i [ n_i \cos(\theta_i) -  n_t \cos(\theta_t) ] =   E_r  [n_t \cos(\theta_t) +  n_i \cos(\theta_i)]\end{equation*}


(9

\begin{equation*}r_s = \frac{E_r}{E_i} = \frac{n_i \cos(\theta_i) -  n_t \cos(\theta_t)}{n_t \cos(\theta_t) +  n_i \cos(\theta_i)}\end{equation*}

Nunc, pro coefficiente reflectionis t, ex eq-1 et eq-4,

(10

\begin{equation*}n_i \cos(\theta_i) [ E_i - (E_t - E_i) ] = n_t E_t \cos(\theta_t)  \end{equation*}


(11) 

\begin{equation*}n_i \cos(\theta_i) [ 2E_i - E_t ] = n_t E_t \cos(\theta_t)  \end{equation*}


(12) 

\begin{equation*} 2E_i n_i \cos(\theta_i) - E_t n_i \cos(\theta_i) = n_t E_t \cos(\theta_t)  \end{equation*}


(13)
 

\begin{equation*} 2E_i n_i \cos(\theta_i) = E_t n_i \cos(\theta_i) + n_t E_t \cos(\theta_t)  \end{equation*}


(14

\begin{equation*}t_s = \frac{E_t}{E_i} = \frac{2 n_i \cos(\theta_i)}{ n_i \cos(\theta_i) + n_t \cos(\theta_t)} \end{equation*}


Hae sunt Aequationes Fresnel pro lumine perpendiculare polarizato (S-Polarization).

Nunc, deducamus aequationes pro lumine parallelum polarizato (P-Polarization).

Pro S-Polarization, aequationes pro campo E et campo B sunt;

(15) 

\begin{equation*}E_i \cos(\theta_i) + E_r \cos(\theta_i) = E_t \cos(\theta_t)\end{equation*}


(16) 

\begin{equation*}B_i - B_r = B_t\end{equation*}


Utimur relationem inter B et E ut eliminemus B. 

 

\[ B = \frac{nE}{c_0} \]


(17) 

\begin{equation*}n_i E_i - n_i E_r = n_t E_t\end{equation*}


  

\[  n_i [E_i - E_r] = n_t E_t \]


 
 

\[ \frac{n_i}{n_t} [E_i - E_r] = E_t \]


Pone hoc valorem in eq-15,

(18) 

\begin{equation*}E_i \cos(\theta_i) + E_r \cos(\theta_i) =  \frac{n_i}{n_t} [E_i - E_r] \cos(\theta_t)\end{equation*}


(19) 

\begin{equation*}n_t [E_i \cos(\theta_i) + E_r \cos(\theta_i)] =  {n_i} [E_i - E_r] \cos(\theta_t)\end{equation*}


(20) 

\begin{equation*}n_t E_i \cos(\theta_i) + n_t E_r \cos(\theta_i) = n_i E_i \cos(\theta_t) -  n_i E_r \cos(\theta_t)\end{equation*}


(21) 

\begin{equation*} n_t E_i \cos(\theta_i) - n_i E_i \cos(\theta_t) = -n_t E_r \cos(\theta_i) - n_i E_r \cos(\theta_t) \end{equation*}


(22) 

\begin{equation*}E_i [n_t \cos(\theta_i) - n_i \cos(\theta_t)] = -E_r [n_t \cos(\theta_i)  + n_i \cos(\theta_t)]     \end{equation*}


(23) 

\begin{equation*}E_i [ n_i \cos(\theta_t) - n_t \cos(\theta_i)] = E_r [n_t \cos(\theta_i)  + n_i \cos(\theta_t)]     \end{equation*}


(24) 

\begin{equation*}r_p = \frac{E_r}{E_i} = \frac{ n_i \cos(\theta_t) - n_t \cos(\theta_i)}{n_t \cos(\theta_i)  + n_i \cos(\theta_t)}\end{equation*}


Nunc, pro coefficiente reflexionis t, ex eq-17

  

\[ n_i E_i - n_t E_t = n_i E_r \]     \[ E_i -\frac{n_t}{n_i} E_t = E_r \]


Pone hanc valorem in eq-15

(25) 

\begin{equation*}E_i \cos(\theta_i) +  [ E_i -\frac{n_t}{n_i} E_t]  \cos(\theta_i) = E_t \cos(\theta_t)\end{equation*}

(26) 

\begin{equation*}E_i \cos(\theta_i) + E_i \cos(\theta_i) - \frac{n_t}{n_i} E_t \cos(\theta_i) = E_t \cos(\theta_t) \end{equation*}


(27) 

\begin{equation*}2 E_i \cos(\theta_i) = \frac{n_t}{n_i} E_t \cos(\theta_i) + E_t \cos(\theta_t) \end{equation*}


(28) 

\begin{equation*}2 E_i n_i \cos(\theta_i) = n_t E_t \cos(\theta_i) +  {n_i} E_t \cos(\theta_t) \end{equation*}


(29) 

\begin{equation*}2 E_i n_i \cos(\theta_i) = E_t [n_t \cos(\theta_i) +  {n_i} \cos(\theta_t)] \end{equation*}


(30

\begin{equation*} t_p = \frac{E_t}{E_i} = \frac{2 n_i \cos(\theta_i)}{ n_t \cos(\theta_i) +  {n_i} \cos(\theta_t)}  \end{equation*}


Compendemus quattuor aequationes Fresnelianas,  

\[ r_s = \frac{n_i \cos(\theta_i) -  n_t \cos(\theta_t)}{n_t \cos(\theta_t) +  n_i \cos(\theta_i)} \]

  

\[ t_s = \frac{2 n_i \cos(\theta_i)}{ n_i \cos(\theta_i) + n_t \cos(\theta_t)} \]


  

\[ r_p = \frac{ n_i \cos(\theta_t) - n_t \cos(\theta_i)}{n_t \cos(\theta_i)  + n_i \cos(\theta_t)} \]


  

\[ t_p = \frac{2 n_i \cos(\theta_i)}{ n_t \cos(\theta_i) +  {n_i} \cos(\theta_t)} \]

Declaratio: Respektare originale, boni articuli digni sunt ad communicandum, si ius violatum est, quaesumus dele.

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