emissivity

Emissivity is a measure of how effectively a surface emits thermal radiation compared to an ideal blackbody, which emits the maximum radiation possible at a given temperature. It is a value between 0 and 1; a higher emissivity means the material radiates heat more efficiently, while a lower value indicates less radiation emission. For example, dull, dark surfaces generally have higher emissivities than shiny, smooth metals. Understanding emissivity helps in assessing heat transfer and temperature measurement, especially in fields like thermography and thermal engineering.