 #1
 28
 2
I am trying to understand diffraction on periodic structured in solid state physics.
Q is the source of the spherical wave. R the vector to the object and R+r the vector to the scattering centre P, which gives us a another spherical wave.
All spherical waves are considered as plane waves due to the big distance between P,B and Q.
The magnitude at P can be described as: ##\Psi_P(t) = \Psi_0e^{i(\vec k (\vec R + \vec r)\omega_0 t)}##
My questions:
1. The magnitude on point Q, which means ##\vec R + \vec r = 0##, is only depending on the time ##t## in ##e^{i\omega_0 t}##. My book(Ibach, Lueth Festkörperphysik) says that it has a fixed phase anytime. According to wikipedia(https://en.wikipedia.org/wiki/Plane_wave#Complex_exponential_form) the phase ##\varphi## is included in ##\Psi_0##. **What does it mean to have a "fixed phase" especially at location Q?**
2. "You can only use this plane wave approach ##\Psi_B## for *a* emission process." my book says, but why is it so?
3. "In real emitters do atoms send many photons with uncorrelated phases. (Exception: lasers)" my book also says. Does that mean the phase of the different photos are independent to each other?
Q is the source of the spherical wave. R the vector to the object and R+r the vector to the scattering centre P, which gives us a another spherical wave.
All spherical waves are considered as plane waves due to the big distance between P,B and Q.
The magnitude at P can be described as: ##\Psi_P(t) = \Psi_0e^{i(\vec k (\vec R + \vec r)\omega_0 t)}##
My questions:
1. The magnitude on point Q, which means ##\vec R + \vec r = 0##, is only depending on the time ##t## in ##e^{i\omega_0 t}##. My book(Ibach, Lueth Festkörperphysik) says that it has a fixed phase anytime. According to wikipedia(https://en.wikipedia.org/wiki/Plane_wave#Complex_exponential_form) the phase ##\varphi## is included in ##\Psi_0##. **What does it mean to have a "fixed phase" especially at location Q?**
2. "You can only use this plane wave approach ##\Psi_B## for *a* emission process." my book says, but why is it so?
3. "In real emitters do atoms send many photons with uncorrelated phases. (Exception: lasers)" my book also says. Does that mean the phase of the different photos are independent to each other?
Attachments

13.4 KB Views: 351

13.4 KB Views: 519