Fantastic! I have one minor question. In this module starting around 6 minutes, you explained at the focal plane they form the diffraction pattern. And in a distance after the focal plane the waves will interfere again to form images. My question is, why single crystal XRD analysis does not collect images directly like EM here, but they collect the diffraction pattern, which is similar to the focal plane spots in EM? Is it because X-ray cannot be easily bent/refocused, so that the diffraction spots are on all directions (sphere), such that they don't have much chances to interfere with each other to form image? Thanks again for the great lecture.
Do the two electron waves mean the waves of two incident electrons, or they are two scattering rays from two different scattering center in sample by only single electron ?
When two electron waves are being added together, they have the same energy because they have the same frequency (23:51). What is it that leads to a difference in amplitude of the electron waves? I would have thought the amplitude also relates to energy, so if it isn't energy of an electron, does that mean a wave with higher amplitude represents more electrons?
As far as I understood my physics (quantum mechanics) classes, let me try to answer this: The energy of a free electron indeed relates directly to its apparent frequency hence wavelength. Possessing this energy can be explained by momentum in its degrees of freedom. In the case of a free electron this is composed (partly) of the speed (momentum) of the electron through space. Electrons have intrinsic angular momentum (spin) too, and to describe the full wavefunction of a free electron, the angular energy is subtracted from the other energy by its momentum (speed) in space. The wavefunction (squared) of a free electron then describes the probability of finding the electron at a certain position in space. The amplitude of the wavefunction does therefore not describe the energy of the electron, although this is a parameter in the wavefunction, but relates to the density of the electron in space. In that sense, yes, you could say that a higher amplitude means that a higher density of the electron(s) is present. A difference in amplitude between two electron wave therefore means that there is a difference in chance of finding the two electrons at that location. For more information, look for "free electron", "wave function", and "frequency of an electron wave".
22:26 "It's 'electronness' that's oscillating" ha ha ha I love it!
Amazing explanation on Fourier and inverse Fourier action of a lens
Just brilliant ... again!
Fantastic! I have one minor question. In this module starting around 6 minutes, you explained at the focal plane they form the diffraction pattern. And in a distance after the focal plane the waves will interfere again to form images. My question is, why single crystal XRD analysis does not collect images directly like EM here, but they collect the diffraction pattern, which is similar to the focal plane spots in EM?
Is it because X-ray cannot be easily bent/refocused, so that the diffraction spots are on all directions (sphere), such that they don't have much chances to interfere with each other to form image? Thanks again for the great lecture.
Do the two electron waves mean the waves of two incident electrons, or they are two scattering rays from two different scattering center in sample by only single electron ?
When two electron waves are being added together, they have the same energy because they have the same frequency (23:51). What is it that leads to a difference in amplitude of the electron waves? I would have thought the amplitude also relates to energy, so if it isn't energy of an electron, does that mean a wave with higher amplitude represents more electrons?
same question
As far as I understood my physics (quantum mechanics) classes, let me try to answer this:
The energy of a free electron indeed relates directly to its apparent frequency hence wavelength. Possessing this energy can be explained by momentum in its degrees of freedom. In the case of a free electron this is composed (partly) of the speed (momentum) of the electron through space. Electrons have intrinsic angular momentum (spin) too, and to describe the full wavefunction of a free electron, the angular energy is subtracted from the other energy by its momentum (speed) in space. The wavefunction (squared) of a free electron then describes the probability of finding the electron at a certain position in space. The amplitude of the wavefunction does therefore not describe the energy of the electron, although this is a parameter in the wavefunction, but relates to the density of the electron in space. In that sense, yes, you could say that a higher amplitude means that a higher density of the electron(s) is present. A difference in amplitude between two electron wave therefore means that there is a difference in chance of finding the two electrons at that location.
For more information, look for "free electron", "wave function", and "frequency of an electron wave".
Please the function of English subtitle ON
Who is the asian guy at 23:57?