Questions related to the perception and measurement of light (primarily in the visible range), its mathematical description, the reproduction of colors by different means, color combinations, etc. Please use the tag [electromagnetic-radiation] if you want to refer to the general form of light.
Questions tagged [visible-light]
5126 questions
524
votes
6 answers
How does light bend around my finger tip?
When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry fingertip.
What causes this? Is it the heat from my…
Daniel A.A. Pelsmaeker
- 4,999
375
votes
29 answers
Why are mirror images flipped horizontally but not vertically?
Why is it that when you look in the mirror left and right directions appear flipped, but not the up and down?
Arlen
- 3,945
189
votes
8 answers
Why do shadows from the sun join each other when near enough?
I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when near the pages of the book, joined up with the…
turnip
- 3,768
181
votes
7 answers
Why do we actually see the sun?
I haven't yet gotten a good answer to this: If you have two rays of light of the same wavelength and polarization (just to make it simple for now, but it easily generalizes to any range and all polarizations) meet at a point such that they're 180…
user22862
168
votes
9 answers
Could Legolas actually see that far?
The video “How Far Can Legolas See?” by MinutePhysics recently went viral. The video states that although Legolas would in principle be able to count $105$ horsemen $24\text{ km}$ away, he shouldn't have been able to tell that their leader was very…
Ali
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- 6
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128
votes
7 answers
Why does the humidifier make a stove's flame orange?
Just like this guy's, the color of my stove's flames were affected by the humidifier as well.
Why does this happen?
Is it a good thing or a bad thing ?
Ilya Gazman
- 2,177
123
votes
7 answers
Why are most metals gray/silver?
Why do most metals (iron, tin, aluminum, lead, zinc, tungsten, nickel, etc.) appear silver or gray?
What makes copper and gold have different colors?
What atomic characteristics determine the color?
Ali Abbasinasab
- 1,849
118
votes
6 answers
Why is glass transparent?
Once I asked this question from my teacher and he replied "Because it passes light.". "And why does it pass light?" I asked and he said, "Because it is transparent.".
The same question again, Why glass is transparent? Why does light pass through it,…
SMUsamaShah
- 5,507
94
votes
4 answers
Why does a yellow object turn white under a yellow light? Shouldn't it turn yellow instead?
Recently I was eating a yellow rice for lunch in a restaurant with only yellow lights. But the rice looked white! I was intrigued by this because I always thought it should look yellow since the yellow pigment reflects only yellow light, but the…
David A.
- 1,039
94
votes
7 answers
Why do metals only glow red, yellow and white and not through the full range of the spectrum?
Why don't metals glow from red to yellow to green to blue etc.? Why only red, then yellow and then white? Shouldn't all wavelengths be emitted one by one as the temperature of the metal increases?
If some metals do glow at with different colours,…
Dieblitzen
- 1,687
92
votes
4 answers
What is the mechanism behind the slowdown of light/photons in a transparent medium?
So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the "vacuum" between the atoms?
Henry
- 1,133
91
votes
2 answers
Why is a laserpointer able to "erase" a glow-in-the-dark sticker?
a while ago I tried to charge a glow-in-the-dark sticker using a simple red laser pointer. It was a large sticker, of the type used to mark emergency exits and fire extinguishers here in Germany. I thought I could draw a picture this way, with…
Toastor
- 791
91
votes
1 answer
Why does my wooden door disperse light into a rainbow color spectrum?
On a clear morning, light comes through this window (viewed from the inside)
It then hits the door on the opposite side (so viewing from the outside the door straight on the other side)
There is nothing particularly special going on.
However, if…
Zach Saucier
- 1,191
90
votes
6 answers
Why is light bent but not accelerated?
Light is bent near a mass (for example when passing close to the sun as demonstrated in the famous sun eclipse of 1919). I interpret this as an effect of gravity on the light.
However, it seems (to me, at least) that light is not accelerated when it…
René Nyffenegger
- 1,143
90
votes
5 answers
Why does a full moon seem uniformly bright from earth, shouldn't it be dimmer at the "border"?
I know the moon is not uniformly grey, it has details, craters, it's not just a colored uniform circle from earth, however, when in a full moon, the intensity of the light received from different parts of the "disc" seems very similar.
Let's define…
Santropedro
- 1,436