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| Radiometry: Transmission of power through an interface | Prev topic | Next topic Fig. 1 |
Transmission of power, dΦ, of radiation within a pencil of rays through an interface between two uniform media with refractive indices m'1 and m'2 must fulfill the law od conservation of energy. Hence:
| dΦi = dΦr + dΦt | (1) |
where subscripts i, r, and t, denote the incident, reflected, and transmitted power, respectively. By using the definition of irradiance, E, and in reference to Fig. 1, we thus have (for example, Hecht E 1987):
| Ei dA1 = Er dA1 + Et dA2 | (2) |
and, by dividing Eq. 2 by Ei dA1, we obtain:
| 1 = |
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+ |
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| = |
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+ |
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| = | r 2 | + t 2 |
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| = | R | + | T | (3) |
where r and t are the incidence angle- and polarization-dependent Fresnel reflection and transmission coefficients, respectively, and where we used Eq. 2 of Transmission of irradiance ... to obtain the second term of the third line in the above equation. Hence, Eq. 3 applies to media with magnetic permeabilities essentially identical to that of vacuum. R and T are the incidence angle- and polarization-dependent power reflection and transmission factors, respectively.
| CITATION: Jonasz M. 2006. Radiometry: Transmission of power through an interface (www.tpdsci.com/Tpc/RdmPowTsm.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 06-Mar-2008 Modified: 06-Mar-2008 Peer-reviewed: PENDING |
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