(20S) and (21S) Intensity and Illumination - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: General Software Library (/forum-13.html) +--- Thread: (20S) and (21S) Intensity and Illumination (/thread-12998.html) (20S) and (21S) Intensity and Illumination - Eddie W. Shore - 05-20-2019 12:48 PM The follow equation relates the luminous intensity (measured in candelas, cd) and illuminance (measured in lux) of a light source. The equation assumes the light source radiates a spherical matter. E = I / R^2 E = illuminance I = luminous intensity R = radius of the sphere's light (meters) LBL A: Solve for E LBL B: Solve for I LBL C: Solve for R Registers: R0 = E R1 = I R2 = R Store the following values in the register and execute the appropriate label. Program: Code: 01  LBL A:  61,41,A 02 RCL 1:  22, 1 03 ÷:  45 04 RCL 2:  22, 2 05 x^2:  51, 11 06 =: 74 07 STO 0:  21, 0 08 R/S:  26 09 LBL B:  61,41,B 10  RCL 0: 22,0 11  *:  55 12  RCL 2: 22,2 13  x^2:  51,11 14  =:  74 15  STO 1: 21, 1 16  R/S:  26 17  LBL C: 61,41,C 18  RCL 1: 22,1 19 ÷: 45 20 RCL 0: 22,0 21  =:  74 22 √:  11 23 STO 2: 21, 2 24 R/S:  26 Example 1: R1 = I = 400, R2 = R = 2. Solve for E, XEQ A returns 100 Example 2: R0 = E = 180, R2 = R = 3 Solve for I, XEQ B returns 1620 Example 3: R1 = I =420, R0 = E = 195 Solve for R, XEQ C returns 1.467598771