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In physics, spectral studies have been observed and quantified since 1822 when Fourier J. (1822) used them in his analysis of thermal conduction. Further, Balmer (1885), studying the hydrogen atom, noticed the existence of the four lengths waveform which characterize the spectrum of the hydrogen atom. Following the research, it determined the number of 364.6 nm that was identified in each hydrogen spectral line. Therefore, Balmer determined the equation to determine the wavelength of the emission or absorption lines. Three years later, physicist Johannes Rydberg generalized Balmer's equation, thus determining the constant Rydberg. Rutherford's model was later improved and in 1913 was introduced Bohr's model and converts justify empirical results in terms of fundamental physical constants. Subsequently, a significant number of physicists approached the spectral analyzes of electromagnetic radiation (in different fields: ultraviolet, X-rays, infrared) and analyzed their characteristics: frequency, amplitude, spectral density. In the economy, the first papers that dealt with spectral analysis emerged in 1960 and consisted of the analysis of seasonal adjustment procedures for time series at macroeconomic level. Starting from the cross-spectral methods were developed methods such as analysis of the movement in the series, the time-frequency methods, etc. The fluctuating nature of the activities of different sectors of activity involves different oscillations in terms of amplitude and frequency, but also oscillations characterized by a higher or lower propagation period, which determines the evolution of economic indicators. We can classify the propagation periods of activities according to the level of the characteristics that determine them in time units (time intervals). Thus, the oscillation frequency will be given by the number of periods of propagation activities. Depending on the oscillation period will determine their average, and the amplitude of oscillation is determined by peak line and the average determined. Starting from the ultraviolet spectrum in physics and the spectral analyzes made by physicists, analogy we find in the economy elements that refer to the fervent oscillations and form "color strips" and "spectrum". To make "spectral analysis" of such a fluctuating process in terms of frequency and amplitude need a sufficient number of numerical data on the evolution of an economic process.

The Spectral Analysis of Labor Force and Profit of Construction Materials Distribution Companies in Romania Analogue Spectrum of Light in Physics