Fluorescent Vs Incandescent---Light Wave Bounce

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naplespete57

naplespete57

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Many moons ago in tech school my instructor taught us that fluorescent lights cause alot less shadows than incandescent because fluorescent light waves bounce wheras incand. light is in a straight line.

Now I tried to explain that to a contemporary with mucho experience and he dared doubt me.

Now that the gauntlet has been tossed I have to back up my statement. I've spent a half hour googling this on the internet to no avail. Any help? Any good links?

Thanks alot!

Pete
 
naplespete57 said:
Many moons ago in tech school my instructor taught us that fluorescent lights cause alot less shadows than incandescent because fluorescent light waves bounce wheras incand. light is in a straight line.

Now I tried to explain that to a contemporary with mucho experience and he dared doubt me.

Now that the gauntlet has been tossed I have to back up my statement. I've spent a half hour googling this on the internet to no avail. Any help? Any good links?

Thanks alot!

Pete
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Incandescent is more like a point source than a fluorescent. Depending on the type of fluorescent, the light emitting portion can be significantly larger -- feet for tubes, versus fractions of an inch for incandescents.
 
tallgirl said:
Incandescent is more like a point source than a fluorescent. Depending on the type of fluorescent, the light emitting portion can be significantly larger -- feet for tubes, versus fractions of an inch for incandescents.
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Yes, a very good explanation. You might say that for resons that Tallgirl pointed out, that the shadows in a scene lit by fluorescent lights are softer than those produced by incandescent lights. But they both of course create shadows. e/m
 
Anecdotal Evidence

Anecdotal Evidence

Color me dazed and confused so far.

However if you hold your hand under a fluorescent light the shadow is minimal, muted, and undefined. If you hold your hand under an incand. the shadow is defined and if you try real hard you can make a Bunny.

This would prove my point to no one..but me
 
Your shadow is muted and undefined because the light source is 4 feet long vs 4 inch diameter. The light is of the same/similar wavelength, but the reflector/refractor will also disperse the lighting photons differently. I'll bet if you look at your shadow under an uncovered, 2 foot long T5HO lamp it will be as sharp as the 100 watt incandescent you are comparing it to.
 
naplespete57 said:
because fluorescent light waves bounce wheras incand. light is in a straight line.

Pete
Click to expand...

That is plain hogwash. Light ALWAYS travel in a straight direction, except when strong gravitational forces bend it, such a black holes. The instructor could be right though, if you consider his head a black hole .....:D
 
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weressl said:
That is plain hogwash. Light ALWAYS travel in a straight direction, except wehn strong gravitational forces bend it, such a black holes. The instructor could be right though, if you consider his head a black hole .....:D
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Sounds a lot like my 3rd-year teacher... I know a lot of information went in to his head, but nothing worthwhile ever came out!....:grin:
 
naplespete57 said:
However if you hold your hand under a fluorescent light the shadow is minimal, muted, and undefined. If you hold your hand under an incand. the shadow is defined
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Yes, but this has _nothing_ to do with incandescent versus fluorescent, and everything to do with the _shape_ of the light source.

Imagine that instead of a 40W fluorescent tube you had a row of the small 5W frosted bulbs. You would see the same minimal and undefined shadow.

Now imagine that you have a single 100W incandescent bulb at one end of a large room, and you are at the other end. Nice, sharp shadows. Replace this bulb with a compact fluorescent lamp, and you will have very similar shadows.

There are probably subtle differences in the ways that materials reflect and diffuse the different colors of light, and fluorescent lamps have different spectra than incandescent lamps, so there are probably small and subtle differences in shadow generation that are separate from bulb shape, but the dominant factor is simply the _shape_ of the light source.

-Jon
 
winnie said:
Yes, but this has _nothing_ to do with incandescent versus fluorescent, and everything to do with the _shape_ of the light source.

Imagine that instead of a 40W fluorescent tube you had a row of the small 5W frosted bulbs. You would see the same minimal and undefined shadow.

-Jon
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Errrm, no. Depending on the number of bulbs you'd see that many well-defined shadow edges.

What makes fluorescent tubes so nice is that the light source is continuous. On a table, centered under a chandelier, place a vase with flowers in it. Your wife will want to know the special occasion, so lie to her. What you'll see are distinct shadows. As you increase the number of bulbs, and reduce the lumens of each, each distinct shadow becomes less sharp because the illumination difference between in and out of shadow is reduced.
 
tallgirl said:
Errrm, no. Depending on the number of bulbs you'd see that many well-defined shadow edges.

What makes fluorescent tubes so nice is that the light source is continuous. On a table, centered under a chandelier, place a vase with flowers in it. Your wife will want to know the special occasion, so lie to her. What you'll see are distinct shadows. As you increase the number of bulbs, and reduce the lumens of each, each distinct shadow becomes less sharp because the illumination difference between in and out of shadow is reduced.
Click to expand...

Errrm, yes.

Infinite number of lightsources placed next to each other with virtual distance between them reduced to zero is what you call continuous light source. The light comes from POINT sources not a linear source. Such source does not exist in physics, even though Hawkins dreams of it every once in a while as it would represent warped time.
 
tallgirl correctly found a hole in the example that I gave. I didn't specify the spacing between the bulbs.

I meant to say 'Imagine that instead of a 40W fluorescent tube you had a 4 foot long row of those small 5W frosted bulbs sitting next to each other so that the glass touches. These bulbs are frosted so that the light source is roughly a sphere 1" in diameter. You would have an incandescent source that is 4 feet long and 1" wide, with dimples in the width every inch. The shadow from this source would be minimal and undefined, and a very good approximation to that of the fluorescent tube.'

There are linear incandescent lamps that look quite a bit like fluorescent tubes; these would be a better comparison.

-Jon
 
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