A 25W lamp can illuminate the scope of what?
Ignoring the air can spread 4000 kilometers (this is the limit of the eye's perception of photons)
According to the 3W. 25W square is 8 square. But there is a lamp size of the illumination range will decline.
If the height of 4 meters is a straight cylinder type lamp can shine a square around 4-6 in general.
It depends on what kind of, the irradiation range relative cross straight tube tube is relatively small, but also the height range of ground distance, the higher the distance with the light irradiation is less light is smaller and more strong light.