Why Does Reflected Light Experience a Phase Change?

• marlon
In summary: .reflection of light always experience a 180 degree phase change when it reflects off of a medium with a higher index of refraction (like water). this is well known and can be proven with calculations.
marlon
Reflected light will experience a 180 degree phase change when it reflects from a medium of higher index of refraction and no phase change when it reflects from a medium of smaller index. This is very well known. However i am wondering why that is ? Can anyone give me some calculations that actually prove this ?

Thanks

marlon

The "Fresnel Relations" in physics-optics give the reflected E' field as
E'=E_{incident}[(n_1-n_2)/(n_1+n_2)] for normal incidence.
This shows the phase change. The FRs are derived in most junior level EM or optics texts. They follow from the BCs on E and H at the interface of two dielectrics.
The transverse components of each are continuous.

The theory of reflection of light is presented in any textbook of optics.I liked and reccomend the bible:M.Born & P.Wolf:"Principles of Optics",any edition,chapter 1,starting with page 36.

Daniel.

Guys, if it is so easy why not give me a specific explanation as to why the phase change happens in this particular case ? Dexter, referring to books is useless because i am never going to read that book. I am asking for an explanation and if you cannot give it then don't post just for the sake of posting...Please...

So my question still stands...Anyone who knows the answer ?

regards
marlon

Marlon,the equation Meir posted states that,for normal incidence,

$$E_{reflected}=E_{incident}\frac{n_{1}-n_{2}}{n_{1}+n_{2}}$$

If $n_{1} < n_{2}$,then $E_{reflected}= - k E_{incident}$ (1)

,where $k=:\frac{n_{2}-n_{1}}{n_{1}+n_{2}}>0$ (2)

Okay.Now,u write,following (1) & (2)

$$E_{reflected}=k E_{incident}e^{i\pi}$$ (3)

Is it any clear?Guess not.I introduce the phases and the polarization vectors,okay,then

$$\vec{E}_{reflected}=\vec{e_{p}}E_{reflected}e^{i\left(\vec{k}_{reflected}\cdot\vec{r}-\omega t\right)}$$ (4)

Using (3),u see where that phase change comes from.

http://scienceworld.wolfram.com/physics/FresnelEquations.html

(For the graph).

Here's a nice course

http://www.ece.rutgers.edu/~orfanidi/ewa/

BTW,it's PHASE.

Daniel.

thanks dexter

1. What is a phase change in terms of light?

A phase change in light refers to a change in the relative position of the peaks and troughs of an electromagnetic wave. This can occur when light is reflected off of a surface, causing a shift in the wavelength and direction of the light.

2. Why does reflected light experience a phase change?

Reflected light experiences a phase change because of the change in medium it encounters when it reflects off of a surface. This change in medium can cause a change in the speed and direction of the light, resulting in a shift in its wavelength and phase.

3. How does the angle of reflection affect the phase change of light?

The angle of reflection plays a crucial role in the phase change of light. When light reflects off of a surface, the angle of reflection is equal to the angle of incidence. This change in direction can cause a shift in the wavelength of the light, resulting in a phase change.

4. Does the material of the reflecting surface affect the phase change of light?

Yes, the material of the reflecting surface can have an impact on the phase change of light. Different materials have different refractive indices, which can cause a change in the speed and direction of the light when it reflects off of them. This, in turn, can result in a phase change of the reflected light.

5. How does the phase change of reflected light impact our perception of color?

The phase change of reflected light can impact our perception of color because it can cause a shift in the wavelength of the light. This shift can result in a change in the color of the reflected light that we see. This is why objects may appear to have different colors when viewed from different angles, as the phase change of the reflected light can alter the colors that are reflected back to our eyes.

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