An experiment has been performed to determine the directional reflection characteristics of electric nonconductors. The test material was fused polycrystalline magnesium-oxide ceramic. Measurements were made for surface roughnesses ranging from 0.16 to 5.8 microns over a wavelength range extending from 0.5 to 12 microns. The test specimens were illuminated by a narrow pencil of rays inclined at either 10 or 45 deg to the surface normal. The reflected radiation was collected at various directions in the hemispherical space over the surface. The experimental results indicate that the reflection characteristics of a given surface approach a diffuse distribution at short wavelengths and a specular distribution at long wavelengths. Increased surface roughness accelerates the former and retards the latter. Moreover, a given surface becomes effectively smoother when illuminated at larger angles of incidence. For the case of incidence at 45 deg, it was found that maxima in the biangular reflectance distribution occurred in angular directions other than the specular; within the knowledge of the authors, such off-specular peaks have not been discussed previously. The measured specular reflectance could be correlated in a restricted parameter range using a theory originally derived for electric conductors.
Skip Nav Destination
Article navigation
Research Papers
Biangular Reflectance of an Electric Nonconductor as a Function of Wavelength and Surface Roughness
K. E. Torrance,
K. E. Torrance
Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minn.
Search for other works by this author on:
E. M. Sparrow
E. M. Sparrow
Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minn.
Search for other works by this author on:
K. E. Torrance
Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minn.
E. M. Sparrow
Heat Transfer Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minn.
J. Heat Transfer. May 1965, 87(2): 283-292 (10 pages)
Published Online: May 1, 1965
Article history
Received:
August 25, 1964
Citation
Torrance, K. E., and Sparrow, E. M. (May 1, 1965). "Biangular Reflectance of an Electric Nonconductor as a Function of Wavelength and Surface Roughness." ASME. J. Heat Transfer. May 1965; 87(2): 283–292. https://doi.org/10.1115/1.3689091
Download citation file:
Get Email Alerts
Cited By
Related Articles
Effects of Roughness of Metal Surfaces on Angular Distribution of Monochromatic Reflected Radiation
J. Heat Transfer (February,1965)
Radiative Properties of Semitransparent Silicon Wafers With Rough Surfaces
J. Heat Transfer (June,2003)
Off-Specular Peaks in the Directional Distribution of Reflected Thermal Radiation
J. Heat Transfer (May,1966)
Effect of Morphology on Spectral Radiative Properties of Three-Dimensionally Ordered Macroporous Ceria Packed Bed
J. Heat Transfer (December,2013)
Related Proceedings Papers
Related Chapters
Extension of the MCRT Method to Non-Diffuse, Non-Gray Enclosures
The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics
The MCRT Method for Participating Media
The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics
Thermal Interface Resistance
Thermal Management of Microelectronic Equipment