LESSON 08
Illumination
How light brightens surfaces.
Frequency1.00×
Amplitude1.00×
Illumination measures how much light falls on a surface. It depends on the source's brightness and how far away the surface is.
Luminous flux & intensity
Luminous flux (lumens) is total light emitted. Intensity (candela) is light per direction.
Inverse square law
Illumination falls off with the square of distance: E = I / d².
Key Formulas
Inverse square law
E = I / d²
E in lux
Real-life applications
- Lighting design for classrooms
- Photography exposure
- Plant grow-lamps
Summary
- Double the distance → one-quarter the illumination.
Check Yourself
Q1.If you double the distance from a light bulb, illumination on a page becomes…