What is the Formula for working out luminous intensity?

Answer 1

Table 1. SI photometry units

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Quantity Symbol[nb 1] SI unit Symbol Dimension Notes Luminous energy Qv [nb 2] lumen secondlm⋅s T⋅J [nb 3] units are sometimes called talbots Luminous flux Φv [nb 2] lumen (= cd⋅sr) lm J also called luminous power Luminous intensity Iv candela (= lm/sr) cd J an SI base unit, luminous flux per unit solid angle LuminanceLv candela per square metre cd/m2 L−2⋅J units are sometimes called nitsIlluminanceEv lux (= lm/m2) lxL−2⋅J used for light incident on a surface Luminous emittance Mv lux (= lm/m2) lx L−2⋅J used for light emitted from a surface Luminous exposure Hv lux secondlx⋅s L−2⋅T⋅J Luminous energy density ωv lumen second per metre3 lm⋅⋅m−3 L−3⋅T⋅J Luminous efficacy η [nb 2] lumen per wattlm/WM−1⋅L−2⋅T3⋅J ratio of luminous flux to radiant flux Luminous efficiency V 1 also called luminous coefficient

Answer 2

The formula for working out luminous intensity is luminous flux divided by solid angle. Mathematically, luminous intensity (I) = luminous flux (Φ) / solid angle (Ω). Luminous intensity is measured in candelas (cd), luminous flux in lumens (lm), and solid angle in steradians (sr).