I have a question which relates to the physics of light. I hope I can explain it well enough for a proper answer! Let's say there is a 15 feet tall light pole 50 feet from my door step. The light pole has a 300W light bulb. Given these info, is there anyway to calculate the amount of light at my door step? Can I say that the light in front of my doorstep, for example, is equal to a 20W light bulb? Can anyone please provide a general formula for me to plug in the numbers. Thanks in advance.