Lect32_[Compatibility_Mode]

# Lect32_[Compatibility_Mode] - Physics 344 Foundations of...

This preview shows pages 1–4. Sign up to view the full content.

Physics 344 Foundations of 21 st Century Physics: Relativity, Quantum Mechanics and Their Applications Their Applications Instructor: Dr. Mark Haugan Office: PHYS 282 [email protected] TA: Dan Hartzler Office: PHYS 7 [email protected] Grader: Shuo Liu Office: PHYS 283 [email protected] Office Hours: If you have questions, just email us to make an appointment. We enjoy talking about physics! appointment. Notices: Since we have time for only one more problem set before Thanksgiving, I will handout Problem Set 11 next Monday. It will be due a week from then at our last class before Thanksgiving. Midterm II at 8:00pm, Thursday, December 2 in MSEE B012

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Recitation Recap Yesterday we discussed the special case of x-ray diffraction by a crystal with angle of incidence equal to the diffracted angles θ θ incidence equal to the diffracted angles. We say diffraction rather than reflection because the x-ray wavelength is comparable to the spacing between atoms, so, a continuum model of the t l tt i i d t E h t tt i di ti 1 2 crystal matter is inadequate. Each atom scatters x-rays in many directions and interference between the scattered waves determines in which directions the x-ray intensity is strong. As we saw in the case of 2-source interference it is useful to think in terms of As we saw in the case of 2 source interference, it is useful to think in terms of ray paths and wave phase to sort out the conditions for constructive and destructive interference. In the figure above, parts of the wave scattered by atoms 1 and 2 that will In the figure above, parts of the wave scattered by atoms 1 and 2 that will interfere in the direction shown are scattered at different times. However, because the extra distance s 2 that an x-ray wavefront reaching atom 2 before being scattered is equal to the extra distance s 1 a wavefront scattered by t 1 t l b f i th tt d b 2 th i t f atom 1 travels before superposing on the wave scattered by 2, the interference between these waves is always constructive in the special case with the angle of diffraction equal to the angle of incidence.