Required materials: Red laser pointer, green laser pointer, gratings labeled #1 through #6, metric rule, extra batteries, tape measure (metric or in inches)
Part 1. Medical X-Ray Films and Analytical X-Ray Films
Examine Figure 1. Both parts of the figure are obtained by using X-rays. Figure 1a is a medical X-ray film, obtained from a dentist's office, whereas Figure 1b is an analytical X-ray film. Can you explain how X-rays were used to obtain each film?
Part 2. The Nature of Diffraction
Background
The purpose of this laboratory is to examine the properties of diffraction (Part 2) and then to use diffraction to identify some clay minerals (Part 3). Part 2 utilizes light diffraction from gratings made of nylon strands woven together; a common use for such gratings is in filtration devices, such as sieves. Light is used here as an analogue for X-rays. Both radiations are part of the electromagnetic spectrum and are essentially identical in diffraction behavior. In contrast to X-rays, however, light is less dangerous, easy to manipulate, and very inexpensive to generate. The use of gratings is also an analogue. The gratings used here are two-dimensional networks of nylon strands, in this case, whereas crystals are submicroscopic gratings that are generally three-dimensional in nature as defined by atoms.
Unit spacings in diffraction.
The geometry of diffraction, or the positions of the diffraction spots (often referred to as peak maxima, diffraction peaks, etc.) is related to the repeating motif. For example, Figure 2a shows
