A photometric system introduced in the 1950s by H. L. Johnson and W. W. Morgan. It is based on the measurement of stellar magnitudes in three wide spectral bands called U ultraviolet, B blue and V visual, which are centred on wavelengths 350, 430 and 550 nanometres, respectively. Colour indices formed by computing U-B and B-V may be used to deduce some of the physical properties of individual stars or groups of stars. To extend the usefulness, more bands were added by Johnson in 1965 extending into the infrared. These are called R, I, J, H, K, L, M and N, ranging from 0.7 to 10.2 micrometres.