Solved: A beam of 72-eV electrons is scattered from a

Chapter 27, Problem 68GP

(choose chapter or problem)

Problem 68GP

A beam of 72-eV electrons is scattered from a crystal, as in X-ray diffraction, and a first-order peak is observed at

25-11 X-Rays and X-Ray Diffraction

In 1985, W.C. Roentgen (1845-1923) discovered that when electrons were accelerated by a high voltage in a vacuum tube and allowed to strike a glass or metal surface inside the tube, fluorescent minerals some distance away would glow, and photographic film would become exposed. Roentgen attributed these effects to a new type of radiation (different from cathode rays). They were given the name X-rays after the algebraic symbol x, meaning an unknown quantity. He soon found that X-rays penetrated through some materials better than through others, and within a few weeks he presented the first X-ray photograph (of his wife’s hand). The production of X-rays today is usually done in a tube (Fig. 25-36) similar to Roentgen’s, using voltages of typically 30 kV to 150 kV.

 What is the spacing between planes in the diffracting crystal? (See Section 25–11.)