this app is a traditional torch or flashlight but it have a new feature: the selective yellow light that is used in the fog. but why use selective yellow light?
selective yellow lamps have consistently over the years been subjectively preferred as "better" in bad weather and lower in glare than white ones. Even now, when most of the world's fog lamps emit white light, the "good fog lamps are yellow" idea still has traction. So is there a real benefit? Or is it just a subjective impression? we probably will never know the vagaries of the answer to this question.
But we know that selective yellow light can improve a driver's ability to see in fog or rain or snow, but not because it 'penetrates fog better' or 'reflects less off droplets'. In fact it's because of the way the human eye processes different colors of light. Blue, indigo, and violet are difficult for the human optical system to process correctly. They are the shortest visible wavelengths and tend to focus in front of our retina rather than upon it.
Within this app You can use your mobile phone as a traditional Flashlight or a Fog light to use in some cases