E field phase matching at interface, deriving Snell's Law

In summary, the conversation discusses the confusion surrounding the unnumbered equation on page 75 of Klein and Furtak's optics book, specifically regarding the absence of arbitrary phase factors. The equation is compared to a similar one in Jackson's Classical Electrodynamics, which simply states that the phases must match at the origin. The individual has struggled to understand this concept and has written multiple pages of equations in an attempt to solve the boundary conditions. The interface being discussed is the z=0 plane. The conversation ends with a mention of Griffiths' explanation in chapter 7.
  • #1
Cruikshank
82
4
I'm studying optics on my own and have gotten very stuck on page 75 of Klein and Furtak, the unnumbered equation. Specifically, I don't understand why there aren't arbitrary phase factors inserted; the equation does not look general enough. I checked in Jackson, 2nd edition Classical Electrodynamics, and on page 279 Jackson simply states in equation 7.34 that the phases have to match at the origin. There isn't much there, just a declaration, and I don't understand why it should be true. Any pointers?

I've gotten nearly everything else in that derivation, but really I must have written 50 pages of equations trying to solve these boundary conditions.

Incoming wave vector k = n - iK (propagation and attenuation) Reflected wave has double prime, transmitted wave has single prime. Klein and Furtak simply write (for E_t, t is tangential, consider it a variable for which x or y can be substituted:)

E_t*e^-i(k_x x) + E"_t*e^-i(k"_x * x + k"_y*y) = E'_t*e^-i(k'_x * x + k'_y * y)

The interface is the z=0 plane, so I see why there are no z factors. But I would have inserted arbitrary phases on E' and E". Why are they not needed?
 
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  • #2
Cruikshank said:
E_t*e^-i(k_x x) + E"_t*e^-i(k"_x * x + k"_y*y) = E'_t*e^-i(k'_x * x + k'_y * y)

The interface is the z=0 plane, so I see why there are no z factors. But I would have inserted arbitrary phases on E' and E". Why are they not needed?

IIRC, Griffiths gives a decent argument (middle of chapter 7 I think).
 

1. What is the concept of E field phase matching at an interface?

The concept of E field phase matching at an interface refers to the process of matching the electric field phase of an incoming wave with the electric field phase of a reflected wave at an interface between two different media. This phenomenon is governed by Snell's Law, which describes how the angle of incidence and angle of refraction of an electromagnetic wave change as it passes through an interface.

2. How is Snell's Law derived from E field phase matching at an interface?

Snell's Law can be derived from E field phase matching at an interface by considering the boundary conditions at the interface. The electric field of an incoming wave must be equal to the sum of the electric fields of the reflected and transmitted waves. By equating the electric fields at the interface, we can derive Snell's Law.

3. What are the assumptions made in E field phase matching at an interface?

There are a few assumptions that are made in E field phase matching at an interface. These include the assumption that the interface is flat and smooth, the media on either side of the interface are linear and homogeneous, and the electric field is perpendicular to the interface. Additionally, the frequency of the electromagnetic wave must remain constant as it passes through the interface.

4. How does E field phase matching at an interface affect the polarization of an electromagnetic wave?

E field phase matching at an interface does not affect the polarization of an electromagnetic wave. The polarization state of the incident wave remains unchanged as it passes through the interface, and the reflected and transmitted waves will have the same polarization as the incident wave.

5. Can E field phase matching at an interface occur if the two media have different refractive indices?

Yes, E field phase matching at an interface can occur even if the two media have different refractive indices. As long as the boundary conditions are met and the assumptions are valid, Snell's Law can still be applied to calculate the angles of incidence and refraction. However, if the difference in refractive indices is too large, total internal reflection may occur instead of transmission.

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