The study of Physics began with the founding of the University. At the age of 28, Henry A. Rowland became the first faculty member when he was appointed Assistant in Physics on December 6, 1875. Rowland had studied engineering at the Rensselaer Polytechnic Institute, receiving the degree of C.E. in 1870 and teaching at Rensselaer until 1875. Once at Hopkins, Rowland equipped a superior laboratory, and assembled a strong core of faculty and fellows for teaching and research.

Rowland's outstanding achievement was in the area of spectroscopy, which remains a specialty in the Department of Physics. He perfected an engine for ruling (inscribing) diffraction gratings, a series of fine parallel grooves evenly spaced on a flat or curved surface at a tolerance much less than the wavelength of light; when light is transmitted through or reflected off of a grating, it is spread out in the order in which its component wavelengths excite the sensations of color vision. Rowland also worked in the fields of calorimetry and thermometry, determining the exact mechanical equivalent of heat (a joule). His other fields of interest were magnetism and electricity. A colleague, Edwin H. Hall, built upon Rowland's work in these areas, discovering the existence of the electromotive force at right angles both to the current flow and its magnetic field, which came to be known as the Hall Effect. In 1880, Hopkins awarded Rowland an honorary Ph.D. for his work -- the only honorary doctor of philosophy ever awarded by Hopkins.

Henry Rowland suffered from diabetes, at that time an untreatable, terminal disease, and he hoped to provide support for his family by developing a telegraph company. During the last few years of his life these activities and his academic duties occupied his time and attention, leaving him little opportunity to pursue the research into theoretical physics which had demonstrated his brilliance. He died in 1901.

One of Rowland's successors in the Department of Physics was Joseph Sweetman Ames. Ames spent his entire academic career at Hopkins, receiving his A.B. in 1886 and his Ph.D. in 1890. Appointed Professor in 1898, Ames assumed the directorship of the Physical Laboratory upon Rowland's death. While not renowned as a brilliant researcher, Ames was dedicated, organized, and had a special flair for teaching. This fit perfectly with his assumption of the leadership role in the department. Ames was an excellent expositor on the work and principles of Rowland's spectrographic research.

During Ames's tenure as professor of physics, he became a member of the Academic Council, later becoming its secretary in 1915. He was keenly interested in various aspects of education and published numerous textbooks in physics, mathematics and theoretical mechanics. In 1919-1920, he served as president of the American Physical Society, of which he was an 1889 charter member. In 1924 he became Dean of the College Faculty and worked on the organization of undergraduate studies, later becoming Dean of the College of Arts and Sciences after resigning his professorship in 1926. In the spring of 1929 he was chosen to succeed Frank J. Goodnow as President of the University, in which office he served until his retirement in 1935. He died in 1943.

Upon Ames's departure as Chairman of the Department of Physics, Robert Williams Wood filled the position. Wood was another of Rowland's fellow researchers who spent more than fifty years with Hopkins as a Professor of Experimental Physics and later Research Professor of Physics. Wood continued to experiment with Rowland's work in diffraction gratings and spectroscopy as well as concentrating on his own studies on the phenomenon of fluorescence. He achieved notable results in the analysis of wavelengths and the behavior of electrons. Wood was also instrumental in the continued production of diffraction gratings for both commercial and private educational use. In addition to his academic career, Wood was an amateur detective, occasionally using his knowledge of science to help the police in solving difficult and grisly crimes; he also enjoyed exposing scientific frauds and hoaxes, although he was not above perpetrating pranks and practical jokes himself.

Wood retired in 1938 and was succeeded as chairman by August Herman Pfund. Pfund had come to Hopkins in 1903 as a graduate student and earned his doctorate in 1906. He became a full professor in 1927, concentrating his studies in the field of light rays and heat radiation. He was a pioneer in the measurement of heat radiation from distant stars and invented a practical instrument which could register the heat of a candle from eighteen miles away. Extremely active in the Optical Society of America, Pfund served as president and later received the society's highest honor, the Frederick Ives Medal, in 1939, for his work with infrared rays. Pfund retired in 1947 and died in 1949.

During the Second World War, many changes in personnel occurred in the department. Faculty size dwindled as professors were summoned by the government to assist in the war effort. Hopkins instituted its own war research laboratories in conjunction with the Office of Naval Research, with research focusing mainly on spectroscopy. A leader in this field, Gerhard Dieke, came to Hopkins in 1930 from the University of Gronigen, Holland, as an Assistant to Wood, who had been impressed by Dieke's article on the Raman Effect in molecular spectroscopy in Nature. Dieke, who had earned his Ph.D. from the University of California in 1926, became a full professor in 1939 and his research broadened to include such problems as developing a method of calibration for photographic plates to use in the spectrochemical analysis of steel. This process was the key to maintaining high quality in the steel industry's war production. The development of the atomic bomb also claimed the attention of Dieke and other Hopkins physicists, J. Alvin Bearden (chairman of the department from 1947 to 1949), Franco Rasetti and Richard Cox.

In 1942, the University opened what became known as the Applied Physics Laboratory in Silver Spring, Maryland. The laboratory's initial assignment, in conjunction with the Office of Scientific Research and Development, was the development and production of a proximity fuze device; this fuze played a major role in winning the war for the Allies. First headed by Dr. Merle Tuve, the laboratory continued in operation after the war and remains one of the foremost laboratories in national defense and missile guidance research.

Following the war the department went through a period of reorganization. The Institute for Cooperative Research was founded in 1947 to coordinate the large number of continuing government research contracts. In 1949, Dieke became chairman of the Department of Physics, leading spectrography into the nuclear age. Research into problems of atomic and molecular structure, x-rays and infrared rays led to many advancements in the field.

Dieke headed the Department of Physics until his death in 1965. After a few years of transition, the chairmanship passed to George Owen, a nuclear physicist who had joined the Hopkins faculty in 1951. Owen earned his Ph.D. in 1950 from Washington University in St. Louis, Missouri. He served as chairman of the Department from 1968 until 1972, when he became the Dean of the Faculty of Arts and Sciences. In 1978, Owen was named Dean of the Homewood Faculty, a position he held until his retirement in 1982; he died in 1984. Owen's work in Physics included conducting research in beta-decay and fast-neutron scattering, as well as overseeing a growing department with a faculty of thirty.

During the 1970s, the Department concentrated its research on atomic physics, spectrography, optical spectroscopy of free atoms, laser physics and atomic processes in plasmas. Other areas of research include nuclear and solid state physics and astrophysics, a field also begun by Henry Rowland in the nineteenth century at Hopkins. Study in astrophysics has grown substantially in the department with the opening of the Space Telescope Science Institute at Hopkins, a project of the Association of Universities in Research Astronomy (AURA), funded by NASA.

Aihud Pevsner, a specialist in high energy physics, served as chairman from 1973 to 1979 and was succeeded by Brian Judd, a theoretical and atomic physicist. In 1985, Lloyd Armstrong became chairman. In 1987, Armstrong was appointed Dean of the School of Arts and Sciences and James C. Walker succeeded him as chairman of the department.