Contact your county Extension agent or land grant university for more specific information on measuring light levels for indoor plants.
Light intensity is defined as the concentration of light waves striking the plant's leaf surfaces.
For optimal growth and flowering, plants require the proper intensity and duration of light. This is true whether you are using sunlight, artificial lighting, or a combination of both. Usually, light intensity and duration are the limiting factors when maintaining plants indoors. The primary reason plants need light is photosynthesis. Photosynthesis is the conversion of light energy to chemical energy by plants.