(a) If a diffraction grating has a resolution of 104 , is it possible to distinguish two spectral lines with wavelengths of 10.00 and 10.01 m? (b) With a resolution of 104 , how close in wavenumbers (cm1 ) is the closest line to 1 000 cm1 that can barely be resolved? (c) Calculate the resolution of a 5.0-cm-long grating ruled at 250 lines/mm for first-order (n 1) diffraction and tenth-order (n 10) diffraction. (d) Find the angular dispersion ( , in radians and degrees) between light rays with wavenumbers of 1 000 and 1 001 cm1 for second-order diffraction (n 2) from a grating with 250 lines/mm and 30. 19-B.

Chapter 11: Calculations with Unit Cells 2/1/16 Polymorphic – substance can exist in more than one structure Xray Diffraction crystallography: determine the structure; finds where each atom sits in 3D Crystals are highly ordered Constructive Interference: brighter, larger amplitude Destructive Interference: dimmer; smaller amplitude *If the difference in distance travelled by wavelength is an integer, then the waves are constructive so the light will be lighter Bragg’s Law: nλ=2dsinθ 2a n = integer (n = 1: first order diffraction; n = 2: second order diffraction, etc.) λ = wavelength (m) d = distance of separation between layers (m) θ = angle of incidence Chapte