Dawn Simulation, Priced in Lux-Minutes: The Ramp Duration and Peak Illuminance a Wake-Up Light Needs at Realistic Pillow Distances

Wake-up lights promise a simulated dawn, but the simulation is delivered at the pillow, and pillow distance is set by furniture, not by the product's specification sheet, which quotes illuminance at a flattering range. This paper applies the inverse-square law to a device rated at a stated 300 lux at half a metre, and computes the light dose of a linear dawn ramp at realistic placements. At the bedside the peak is 300.0 lux and a 30-minute ramp delivers 4500 lux-minutes; across the room at 1.8 metres the peak collapses to 23.1 lux and the same ramp delivers 347 lux-minutes, far below a stated effective band of 2500 to 7500. Reaching the band's middle from across the room would need a ramp of 432.0 minutes. Placement, the paper shows, is not a detail of the therapy — it is most of it. This study is simulated, not measured.