2. Conveying something that is bright, glowing, and shining: The radiant sun came out from behind the storm clouds.
Laura's radiant behavior expressed her genuine pleasure when her friend graduated with honors from her high school.
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2. A radiometric term for the rate at which radiant energy in a radiation field is transferred across a unit area of a surface (real or imaginary) in a hemisphere of directions.
In general, irradiance depends on the orientation of a surface. The radiant energy may be confined to a narrow range of frequencies (spectral or monochromatic irradiance which is characterized by a single frequency) or integrated over a broad range of frequencies.