11 posts tagged with light and physics.
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Calculating radiation received at distance from light source?

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]
posted by Joey Buttafoucault on Dec 16, 2014 - 6 answers

Same as it ever was?

Is the speed of light constant on the timescale of the universe? [more inside]
posted by Orange Pamplemousse on Mar 14, 2012 - 12 answers

Filter that makes laser beam visible?

Are there types of laser light, color or wavelength, whole beam can be seen in daylight conditions with a special eyeglass filter? [more inside]
posted by pallen123 on Mar 6, 2012 - 11 answers

I don't get this... how can light have momentum?

How can light have momentum? [more inside]
posted by dougrayrankin on Dec 13, 2010 - 9 answers

A 20 million candle power lighthouse

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?
posted by westerly on Jun 8, 2010 - 20 answers

Does one 200 watt bulb put out as much or more light than ten 20 watt bulbs?

Does one 200 watt bulb put out as much or more light than ten 20 watt bulbs? [more inside]
posted by leemajors on Aug 14, 2009 - 23 answers

Why are incandescent lights white?

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.
posted by bdc34 on Oct 7, 2008 - 5 answers

Is there a minimum amount of power required to sustain a given bandwidth?

What, if any, is the relationship between bandwidth and power? [more inside]
posted by odinsdream on Nov 19, 2007 - 14 answers

Please let me out of the parking garage.

Do the green light triggers for motorcycles actually work? [more inside]
posted by electroboy on Nov 16, 2007 - 11 answers

What would happen if you could create a perfect two-way mirror into a sphere?

What would happen if you could create a perfect two-way mirror into a sphere? [more inside]
posted by Lownotes on Oct 30, 2007 - 12 answers

Why do porous objects appear darker when wet?

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?
posted by fvw on Dec 12, 2003 - 7 answers

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