How do I calculate the radiation energy that a surface / object receives at distance d from a light source of power W watts? I'm familiar, in theory, with the inverse square law but need help thinking about how to apply it. [more inside]
Is the speed of light constant on the timescale of the universe? [more inside]
Are there types of laser light, color or wavelength, whole beam can be seen in daylight conditions with a special eyeglass filter? [more inside]
How can light have momentum? [more inside]
I have a candle and its brightness is exactly one candle power or candela. If I buy a 10,000 candle power torch/flashlight, does that mean it's 10,000 times brighter (and what does that mean) or that I can see it 10,000 times further away? Are these the same thing and why do they seem unbelievable?
Does one 200 watt bulb put out as much or more light than ten 20 watt bulbs? [more inside]
Why does an incandescent light bulb have an broad, continuous spectra when viewed with a spectrometer? Why doesn't it have some lines like a sodium lamp? I guess I'm asking why photons come off of a black body and why are their wavelengths spread out. Bonus points for clarity and accessibility of the answers.
What, if any, is the relationship between bandwidth and power? [more inside]
Do the green light triggers for motorcycles actually work? [more inside]
What would happen if you could create a perfect two-way mirror into a sphere? [more inside]
Why do porous objects (wood, textile, hair, etc) appear darker when wet then when dry? A googling gave me this ("surface reflection and refraction"), but that doesn't sound entirely reasonable, as it merely talks of light being scattered, but the light in question is already diffuse. This also gives some suggestions, but nothing conclusive. Any chem/physics MeFiers know this?