The ‘Inverse Square Law’

For those who are not already familiar with the ‘Inverse Square Law’ and how it affects the magnitude of light intensity falling on a surface, you may find this short article illuminating.

So what does it mean?

The inverse square law states: ‘the Intensity of illumination produced by a source varies inversely as square of the distance from this source’. What does this mean exactly? Well… if you half the distance from the light source to a plant, you will increase the light intensity by a factor of four.

Conversely, in accordance with the inverse square law, every millimeter further away from the surface that the light source is, the efficiency will fall by the square of that distance assuming a desired constant PPFD value. In other words, the distance from a light source greatly affects the amount of photons or energy absorbed by plants through photosynthesis.

Why is this important to understand for growers?

When it comes to growing, this simple rule can have a magnified effect on the efficiency of your growth, and the choices you make when purchasing the lighting for your indoor set up. Growers generally know that plants require quantum energy in the form of “photons” to stimulate photosynthesis and production of the necessary nutrients to live. This energy must come from a source that provides the correct wavelengths and, importantly, the correct intensity that plants require.

How does this influence grow lighting decisions? 

All plant species require differing amounts of PPFD at various stages of their development, which has been accomplished by simply increasing power when it comes to traditional lighting fixtures such as Metal Halide and Sodium lamps. Typically, these lighting setups are very costly, energy inefficient, and have short lifespans. This lack of agility in current light fixtures means they require significant support and hanging infrastructure, making the adjustment of distance to plant canopy problematic. Traditional lights are successful in achieving the end result, however, they are unable to maximise the benefits of modern LED lighting as an adjustable and cost efficient solution.

Our grow lights make tending to plants easy and energy efficient by using a smart wire cable system to control distance (PPFD), a dimmer function to adjust light intensity (PPF) and a patented heatsink to keep it cool. So when considering what kind of light you need for your indoor plants, it’s worth thinking about LED as an efficient, safe and long term solution.

Leave a Reply