A wake-up light is actually a quite simple device in your bedroom. It’s an alarm clock, also known as a sunrise alarm clock that wakes you up with a combination of light and sound.
Waking you up
The model that I have and use myself is a Philips HF3480 and this one has a light that gently starts to glow 30 minutes pre the time I set the alarm at. So if I set the alarm at 07.15, the light will gently start at 06.45 at the lowest intensity which is 1/20, and gradually over a 30 minute period, it will get brighter and brighter, right up to the intensity that you set it at last time you used it. Which in my case usually is 20 (20 is max), I usually keep the light at full strength.
A rough illustration of the 30 min wake up process
So when the light is finally at full strength at 07.15, the sound also starts (the sound alarm is optional) the sound is the same as the light, it will be the same level for the alarm, as it was last time you used it. As for myself, I keep the light intensity at 20 (max) and the sound volume at 5-7 on my favorite radio channel.
Many wake up lights from Philips, (others as well) contains a function called dusk simulation, this is a sleep assistant that will help you fall asleep by gradually lowering the intensity of the light and sound.
This simulation of the sun going down is naturally making you sleepy ( trust me it works ). And the chilling sound that is gradually getting lower and lower is a very good recipe for sleep well. Using this function if you don’t feel very sleepy when you go to bed.