Bouguer-Lambert Law Research Articles

Submicron thickness calibration of vapor-deposited SiO2 films by infrared spectroscopy

Infrared transmission spectra of a series of SiO2 films vapor deposited on silicon from SiH4 and O2 at 450 °C have been studied as a function of film thickness in the submicron range from 1000 to 9000 Å. Absorbances of band maxima observed in the frequency range 250–1400 cm−1 are shown to obey the Lambert-Bouguer's law in both as-deposited and heat-treated (800–1200 °C) materials. Apparent absorption coefficients calculated for the transmission mimima at 1060, 800, and 450 cm−1 are 2.5 ± 0.1 × 104, 0.24 ± 0.02 × 104, and 0.74 ± 0.02 × 104 cm−1 for as-deposited films and 3.4 ± 0.1 × 104, 0.34 ± 0.02 × 104, and 1.06 ± 0.02 × 104 cm−1 for heat-treated films, respectively. The thickness of SiO2 films as-deposited at 450 °C as well as heat treated to 800 °C and above can be determined nondestructively using the present absorbance data.

Determining the current density of the electrode spots of an electric arc

The energy balance and the Lambert-Bouguer law are used to obtain a mathematical relationship between the current density for the electrode spots of a carbon arc and the current. Theoretical calculations are confirmed by experiment.

Solar Variation and the Weather

NEARLY a century ago three pioneers, Sir John Herschel, Pouillet, and Forbes, laid the foundations of the measurement of solar radiation. Each devised an instrument for measuring the heating effect of the solar rays and used it diligently. Pouillet and Forbes availed themselves of the law of extinction of light, which had been independently discovered about 1760 by Bouguer and Lambert, to calculate the intensity of the solar rays, as they would be outside our atmosphere. Forbes's researches in the Alps proved that this law is not strictly applicable to the sun's rays as a whole, and he was led to believe that the value of the so-called solar constant of radiation was as high as 2.85 calories per sq. cm. per mm. Pouillet's value, based on the assumed validity of the Bouguer-Lambert law, was 1.76 calories.