The figure below is the emission spectra of a tungsten-halogen lamp operating at 3100K. You may calculate the emission spectra for any black body radiator using Plank's Law for spectral radiant exitance from a non-perturbing aperture in a black body. (See ) The Excel spreadsheet included with this handout on the CH332 lab webpage will assist with these calculations. We will measure the relative irradiance of several light sources in the Museum of Art. Irradiance is the amount of energy at each wavelength emitted from a radiant sample. Absolute irradiance is the measure of light in absolute terms. Relative irradiance is a comparison of the fraction of energy the sample emits and the energy the sampling system collects from a lamp with a blackbody energy distribution (normalized to 1 at the energy maximum). Relative Irradiance is calculated as follows: where RI is the relative irradiance, S is the signal, R is the reference spectra (typically a W-halogen source at 3100K), D is the instrument dark and Rc is relative energy of the reference spectra calculated from the user defined color temperature. At first it seems odd to scale the signal by the reference signal, Rc. However, Rc is the relative energy so all the output is scaled by photon energy, a direct measure of the light available to your eye. The attached spreadsheet allows you to calculate Rc for any black body () .
The figure below is the emission spectra of a tungsten-halogen lamp operating at 3100K. You may calculate the emission spectra for any black body radiator using Plank's Law for spectral radiant exitance from a non-perturbing aperture in a black body. (See ) The Excel spreadsheet included with this handout on the CH332 lab webpage will assist with these calculations. We will measure the relative irradiance of several light sources in the Museum of Art. Irradiance is the amount of energy at each wavelength emitted from a radiant sample. Absolute irradiance is the measure of light in absolute terms. Relative irradiance is a comparison of the fraction of energy the sample emits and the energy the sampling system collects from a lamp with a blackbody energy distribution (normalized to 1 at the energy maximum). Relative Irradiance is calculated as follows: where RI is the relative irradiance, S is the signal, R is the reference spectra (typically a W-halogen source at 3100K), D is the instrument dark and Rc is relative energy of the reference spectra calculated from the user defined color temperature. At first it seems odd to scale the signal by the reference signal, Rc. However, Rc is the relative energy so all the output is scaled by photon energy, a direct measure of the light available to your eye. The attached spreadsheet allows you to calculate Rc for any black body () .
Color-and-Art1.docx