1. Gratings

2. Double Slit Resolution  The bright bands from a double slit are wide. Exact maximum difficult to determine  There is a broad area with some constructive interference.

3. Multiple Interference  More slits create a narrower region of constructive interference. Same relationship

4. Diffraction Grating  A grating consists of a large number of uniformly spaced slits. Measured in slits per cmMeasured in slits per cm Example: 50,000 /cm equals 200 nm spacingExample: 50,000 /cm equals 200 nm spacing  Though it uses interference, it is called a diffraction grating. Large number of scatterers, like diffractionLarge number of scatterers, like diffraction

5. Reflection Grating  Closely spaced ridges can form a grating for reflection.

6. Crystal Scattering  Atoms in a crystal are arranged in uniform layers. Spacing similar to x-ray wavelength.Spacing similar to x-ray wavelength.  The layers can act as a reflection grating.  The path difference for a reflection grating is twice the separation.

7. X-Ray Diffraction  For crystals in random orientation the x-rays will diffract in circles.

8. Bragg’s Law  The angles of the diffraction rings are used to determine the crystal spacing. next