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Electromagnetic radiation, specifically the range of frequencies visible to humans ("visible light").

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70 views

Why is 450 nm monochromatic light perceived as blue or violet depending on its intensity?

Trying to do some color matching I purchased a 450 nm laser. I expected monochromatic light of this laser to have similar properties to those of all others I've already played with — 808, 640, 520, ...
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0answers
35 views

Can low melatonin levels and/or LED lights cause or exacerbate macular degeneration?

I have two questions that may or may not be interconnected. My first question is: Does melatonin prevent macular degeneration? Could low melatonin levels (caused by blue-rich light exposure in the ...
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0answers
26 views

What happens when pure chlorophyll A absorbs blue light?

When pure chlorophyll A is put in the presence of only blue light, what happens? My guess is that the extra energy is released as heat/kinetic energy, and then the electron has dropped to the lowest ...
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1answer
28 views

Why did we evolve to be able to see this specific set of wavelengths only? [duplicate]

It is understandable that life didn't evolve the capability to sense all wavelengths of light, it simply didn't need it. My question is, why did it evolve the set of wavelengths it has, for example, ...
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1answer
48 views

Does night mode on iPhone really help?

Okay so I know that night mode is supposed to filter out blue light that is bad for the eyes, but is it really more helpful than annoying? At night I do use it when I’m on the phone but it doesn’t ...
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0answers
28 views

Are asian eyes better at sun protection?

Today I have visited a very popular tourist place in Tokyo. It was a very sunny weather and there were HUGE crowds of Japanese tourists and I was one of very few Europeans. I have noticed a surprising ...
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0answers
15 views

What is the difference between GFP and rhodopsin?

GFP and Rhodopsin are both fluorescent proteins. What is the main difference between GFP and Rhodopsin in terms of how they work? I know that their excitation and emission wavelengths are different, ...
2
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1answer
48 views

What photoreceptors are necessary to permit infrared vision?

Humans have red green and blue photoreceptors allowing them to sense colours in the spectrum of about 400-700nm. Certain proteins allow for the extending of wavelength range in the RGB receptors, this ...
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0answers
110 views

Can light destroy auxin?

In my biology textbook, it says that plants grow towards light because auxin is laterally transferred from the light side to the shaded side, so more auxin stimulates growth and hence the plant bends ...
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0answers
51 views

What amount of light energy is required to produce one O2 molecule? How about one molecule of NADPH?

I know that for each O2 molecule, a total of 8 photons are required (4 per photosystem). Would the amount of light energy required be E=hc/wavelength using 680 and 700? Or would the energy from the ...
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0answers
268 views

effect of infrared light to eyes and skin?

Recently some new "head mounted displays" which are wearable devices for augmented and virtual reality for industrial, research and entertainment purposes have added infrared light emitting diodes ...
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0answers
23 views

Are natural daylight lamps for Seasonal Affective Disorder just about the color temperature?

I've seen many expensive lamps made for people who have Seasonal Affective Disorder (SAD) and/or who live in regions where there isn't much daylight during the winter. I'm wondering if the benefit of ...
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2answers
61 views

Do Vaccinium membranaceum plants need a minimum amount of darkness per 24 hours?

I have Vaccinium membranaceum (black huckleberry) seedlings growing in a greenhouse. I have the option of providing fluorescent light to the plants 24 hours a day. However, it has occurred to me that ...
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2answers
509 views

Why do most plants reflect green and others other colors?

I have read that chlorophyll absorbs red and blue. As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of ...
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0answers
11 views

Energy transfer to reaction centre in higher plants

In a photosystem, the accessory pigment molecules in the LHC(light harvesting complex) absorb the quanta from different regions of PAR(photosynthetically active radiation) , their electron gets ...
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0answers
25 views

Mobile carriers of Light reaction in higher plants

The hydrogen carrier PQ and the electron carrier PC are the mobile carriers in light reaction facilitating electron transfer from PS II to PS I during non-cyclic process. My question is - How do ...
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2answers
51 views

Reaction centre in Photosystems of higher plants

In photosystems of higher plants, there are about 250-400 pigments (number wise) in a particular photosystem. Out of which,approx 170-180 pigments are of chlorophyll a molecules. And any one of them ...
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0answers
22 views

Does iris color effect the amount of light that reaches photosensitive ganglion cells?

Does eye color (of iris) have any effect on the amount of light reaching retina cells and hence effect melatonin production?
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0answers
20 views

Can household pests be detected by IR cameras or UV lighting?

As I understand, insects are mostly cold blooded, but since they move around and have some metabolism, I was wondering if it would be possible to notice them (or their larvae or eggs) against the ...
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3answers
1k views

Blue light in a fridge. Is it really beneficial or just marketing?

Recently while visiting a shop with electronics I saw a fridge with a huge advertisment sticker going more or less like this: There's blue light source in this fridge so there will be less bacteria ...
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1answer
47 views

Myopia & the Blur Effect

I know myopia is caused by elongation of the eyeball. When the eye is too long, light entering the eye balls falls in front of the retina instead of on it. However I do not quite understand how this ...
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1answer
238 views

Question to the color scientists

I have a question. if you look at these two spectral diagrams (SPDs) from two different televisions that is calibrated to the same white point (D65) 6500K with a spectrometer. The problem is that ...
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0answers
76 views

Insects are attracted to light, what if the light is too bright?

Insects are known to approach light sources. I know that they use it as navigation tools, by maintaining a constant angle between their path and the light beam. However, if a light source is ...
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0answers
602 views

Does Rüppell's Griffon Vulture Have Greatest Vision Acuity? (Small Carrion Spotted at 10 km+?)

Synopsis: Some sources seem to imply the Rüppell's (griffon) vulture (Gyps rueppelli) can see objects at a distance in excess of 10 km -- roughly three times the ...
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2answers
323 views

Cerebral activity during exposure to non - visible light

Our eyes only have the ability to sense light within a certain spectrum. My understanding is that particular frequencies energize specific cells in our eyes, each responsible for a different "color". ...
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1answer
587 views

If mantis shrimp have 16 photoreceptors then how many other colors on the spectrum are there? [closed]

Mantis shrimp have 12 to 16 photoreceptors and humans have 2, and in rare occasions even 3. But if mantis shrimp can see 16, how many other colors are out there? How many photoreceptors is possible? ...
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1answer
1k views

Why do stomata close in low intensity light?

Stomata close during high intensity light to prevent excessive transpiration but why did they close during low intensity of light? Please explain in easy- understand language because i'm in just 10th ...
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0answers
44 views

What do I need to do to make a Reverse colorblind image?

As a 15 year suffering from moderate Protan colorblindness, I've wanted to find any advantages of colorblindness. I discovered there are Reverse colorblind tests, which only colorblind people are able ...
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3answers
3k views

Photosystem 1 and 2; P680/P700; Chlorophyll a/b

I am getting slightly confused about how the above relate to each other. My current understanding is that P680 and P700 refer to the primary pigment reaction centres in Photosystems 2 and 1 ...
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0answers
158 views

Can human perception differentiate between monochromatic and polychromatic light?

Maybe monochromatic is not the right word, what I mean is light consisting of a single wavelength (i.e. a spectral color) versus light composed of photons of multiple wavelengths (intermediate color). ...
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1answer
397 views

Are two colors (red + blue) necessary for LED grow lights, or would either color be sufficient?

Below are some chlorophyll absorption spectra from other answers here. There is strong absorption at both the blue/violet end, and the red end of the spectrum, and presumably both of these contribute ...
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1answer
699 views

What is the biological potential for vision of wavelengths outside the human visual range?

Humans eyes have evolved to perceive light only between approximately 350-700nm, because that form of light is most common to our lifes. Other animals can perceive lights with slightly different ...
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2answers
3k views

Why do I still see a bright light after looking directly at it?

When you look directly at a bright light, maybe accidentally when looking at the sun, the shape of the image may persistently be perceived even after you look away. Does this image persistence have ...
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2answers
124 views

Do different species of bacteria have distinct absorption bands? [closed]

Do bacteria of different species absorb different wavelengths of light? How different? Most of my searching has lead to topics about Optical Dispertion which seems to be species independent as ...
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1answer
259 views

Why are we able to differentiate between colored objects without the presence of light?

Rods help us to see during the dark. We can see colour of the object when it reflects light. But in a dark room(room of any color but the light is switched off and it is night),we still can ...
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0answers
88 views

Why do we fear the night? [duplicate]

I always feel more afraid in the dark than in light conditions. Is this a common phenomenon in all the people? Does it have biological underpinnings?
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0answers
30 views

Spectroscopy on plant leafs

I'm trying to do spectroscopy readings on plants where I shoot electromagnetic waves and look at their signature/profile. I want to be able to do this at a distance, in the field and on live plants ...
4
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1answer
180 views

What is blue light?

What is the "blue light" often discussed in relation to human melatonin production, sleep/wake cycles, etc.? A Google search seems to define it as light of a particular wavelength, suggesting that it ...
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1answer
397 views

Why are fearful stimuli more powerful at night?

For example, horror movies appear to be scarier when viewed at night than during broad day light. Does light have any role in this phenomenon? Are there changes in hormones at night versus during ...
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0answers
74 views

What wavelengths of lights do plants need to grow?

So, I found a list of L.E.D.'s from Cree here (the company seems to be known for efficiency, they power most of the bicycle lights that I know of) is selling a line of lights designed for growing ...
7
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1answer
950 views

Can “red” cone cells actually see much red light?

In electronics, the most common color scheme is the "red-green-blue" (RGB) scheme. This choice is often justified by claiming that the long- (L), medium- (M), and short- (S) type cones in the human ...
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0answers
716 views

Why does vision gradually becomes dimmer in bright setting?

I don't know if this is only happens to me, but if I am in a well lit room and I stare at one point or just look at one area without moving my eyes around my vision in that specific light setting ...
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0answers
305 views

Is there a meaningful difference between direct and indirect light

I don't see a basis for a distinction, but I've heard several people distinguish between direct and indirect light for people, claiming that indirect light would be better in many cases. "Direct" ...
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0answers
97 views

What kinds of light attract moths best?

On average, do we know what kinds of lights attract moths best? LED, filament bulb, candle...? And what about colour? Does that matter? thanks
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1answer
95 views

Using UV to kill bacteria in shoes

I see that UV-C is the best to kill bacteria generally. We are interested in using to kill off odor in shoes. What illuminance is needed to kill most bacteria with UV-C? Thanks!
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1answer
71 views

short-day facultative plant, abrupt change to photo period

What happens biologically to a short-day facultative plant that is a few weeks into its short day (flowering) photo period and is suddenly given a 24 hour period of light? Does anything change ...
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1answer
87 views

Why is flash light harmful to what aquatic life forms?

When visiting an aquarium, it's often not allowed to take photographs with a flashlight on. It is said that the flash light with very high intensity is harmful to the displayed life forms. I respect ...
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1answer
15k views

Why does sunburn cause fever?

Today I found out that sunburns can cause fever. What I don't understand is how/why? In my understanding fever is the side effect of an immune reaction against an intruder, mainly bacteria (though I ...
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0answers
3k views

Why do I see the world in blue when I open my eyes? [closed]

So I was standing outside, waiting for the train. I was tired so I closed my eyes for a while. Then when I opened them, the world was a lot more blue than it normally is - why is this? I tried it a ...
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1answer
35 views

Influence of artificial sunlight on the human body

In a hypothetical scenario, where a large, permanently manned craft is in a continual orbit, and natural sunlight cannot be used as the craft may keep moving and turning, artificial sunlight is used ...