If the luminous intensity of a source of light in some direction is one candela, the irradiance of a point on a surface that is closest to the source is \(1 \text{lm m}^{-2}\) if the distance is one m...If the luminous intensity of a source of light in some direction is one candela, the irradiance of a point on a surface that is closest to the source is \(1 \text{lm m}^{-2}\) if the distance is one metre, \(1 \text{lm cm}^{-2}\) if the distance is one cm, and \(1 \text{lm ft}^{-2}\) if the distance is one foot.
