MEASUREMENT OF NORMAL SPECTRAL EMISSIVITY OF LIQUID COPPER

The normal spectral emissivity of copper in solid and liquid states wa s measured at 1 273 to 1 673 K with wavelength during 400 to 850 nm. T he ratio of radiation intensity to that at a reference wavelength of 6 50 nm was measured in order to avoid the difficulty of simultaneous me asurement of the radiation intensity from a black body. The emissivity of copper increases in solid state and decreases in liquid state with increasing temperature and decreases with increasing wavelength in bo th states. At the melting point of 1 358 K, the emissivity at 650 nm d iscontinuously increases from 0.123 in solid to 0.143 in liquid.