Simplify the following text for a Grade 9 native English-speaking person.
Original: In 1915 father and son were jointly awarded the Nobel Prize in Physics for their studies , using the X-ray spectrometer , of X-ray spectra , X-ray diffraction , and of crystal structure .
Simplified: He invented the X-ray spectrometer , and began work with his son . Together they founded the new technique of X-ray crystallography , for which they won the Nobel Prize in Physics for 1915 .