Sentence:  In addition to the basic programs in <WSD>wavelength</WSD> standards , spectroscopy , solid state physics , interactions of the free electron and atomic constants which are necessary to provide the foundation for technological progress , the Bureau has strengthened its activities in laboratory astrophysics . 
Meaning of the word marked with <WSD> tags:  the distance (measured in the direction of propagation) between two points in the same phase in consecutive cycles of a wave