sentence: Physicist think about undulators both using classical physics and relativity.
sentences_after: This means that though the precision calculation is tedious the undulator can be seen as a black box. An electron enters this box and an electromagnetic pulse exits through a small exit slit. The slit should be small enough so that only the main cone passes, so that  the side lobes may be ignored.
concept_name: physicist
headings: Undulator
categories: Synchrotron instrumentation