To coincide with our Light issue, light aficionado Xander Cadisch writes…
Understanding the science of wavelengths to transform your design.
Xander Cadisch
We live bathed in an ocean of light, yet rarely consider how its invisible waves shape our very biology. Modern research reveals what ancient healers intuited—that light isn't just something we see, but a vital nutrient that regulates our cells, hormones, and nervous system. The implications for how we design our spaces are profound.
At the heart of this revelation lies a simple truth: different colours of light act as distinct biological signals. Take red light, for instance. With wavelengths between 630-700 nanometres, it penetrates deep into our tissues, stimulating mitochondria—those tiny power plants within our cells. This isn't speculative science, it's therapy approved by regulatory bodies like the FDA, now used to accelerate wound healing and ease arthritis pain. Hospitals are beginning to harness this knowledge, installing red light panels in recovery rooms where patients benefit from its regenerative properties.
Then there's blue light—the double-edged sword of our modern world. During daylight hours, those 450-495 nanometre waves boost our alertness and sharpen focus, which explains why cool white lighting works so well in offices and schools. But as evening falls, this same wavelength becomes disruptive, tricking our brains into thinking it's still daytime. The consequences are measurable. Just two hours of evening blue light exposure can delay melatonin production by over an hour, stealing precious deep sleep from our nights. The solution isn't to demonise blue light, but to respect its rhythm—using it strategically by day while transitioning to warmer tones after sunset.
Perhaps most surprising is green light's emerging role in pain management. While all light can aggravate migraine sufferers during attacks, researchers at Harvard Medical School discovered something remarkable. A very specific shade of green (around 525nm) actually reduces photophobia. Patients in clinical trials reported significantly less pain when exposed to this narrow band of green compared to other colours. It's a finding that could transform how we design lighting for healthcare facilities and homes alike.
Yet light's power extends beyond individual colours. The real magic happens in how these wavelengths interact throughout the day—what scientists call our circadian rhythm. Morning light rich in blue tones helps us wake up naturally, while the golden hues of afternoon signal our bodies to start winding down. Modern lighting often ignores this dance, bathing us in the same harsh white glow from dawn to midnight. The consequences aren't just poor sleep—chronic circadian disruption is now classified as a probable carcinogen by the International Agency for Research on Cancer, particularly for night shift workers.
The solution lies in what lighting designers call "human-centric lighting"—systems that dynamically shift colour temperature and intensity to mimic natural daylight cycles. In a London office trial, employees under such adaptive lighting reported 20% better sleep quality and higher daytime energy. At a German hospital, circadian-aware lighting reduced patient recovery times by nearly a third compared to standard fluorescent setups.
What does this mean for how we design everyday spaces? In homes, it suggests layered lighting—bright, cool task lights for morning productivity, transitioning to warm ambient fixtures by evening. In schools, it means maximising daylight while using tuneable LEDs to maintain focus. In healthcare settings, it implies prescribing specific light "doses" as part of treatment plans.
The future of lighting design isn't just about aesthetics or energy efficiency—it's about creating environments that actively support our biology. As we learn to harness light's full spectrum wisely, we open the door to spaces that don't just look beautiful, but help us sleep deeper, heal faster, and live better. This is the promise of light-aware design, not merely illumination, but nourishment for body and mind.
Look out for the Review of his book “The Light Within us” in the 15th issue of The Journal of Biophilic Design.
References
Red Light Therapy - Hamblin, M.R. (2017). AIMS Biophysics, 4(3), 337-361, FDA 510(k) Clearance Database (2020).
Blue Light & Circadian Effects - Harvard Health Letter (2014), IARC Monograph 124 (2020).
Green Light & Migraines - Noseda et al. (2016). Brain, 139(8), 1971-1986.
Circadian Lighting - CIE S 026:2018 Standard; Mottram et al. (2019). Lighting Res. & Tech., 51(4), 557-575.
Fractals & Stress - Taylor et al. (2018). J. Environ. Psych., 57, 1-10.
Technical Standards - IEEE PAR1789-2015 (LED flicker).