Questions tagged [light]

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

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Why doesn't the rate of photosynthesis increase with increasing light energy (frequency)? [duplicate]

Why doesn't the rate of photosynthesis increase with increasing light energy (frequency)? I know that green light is not absorbed by chlorophyll, yet I am confused as to why this certain "...
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Do SILK fibres let light pass through it?

The reason given by Wikipedia for silk fibres being lustrous is that: Silk fibres have triangular prism-like structure, which allows them to refract the incoming light at different angles. By my ...
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What are the physiological effects of retinal exposure to 380–400nm light?

There are two categories of sunglasses: UV380 sunglasses block all light with wavelength 380nm or lower, while UV400 sunglasses block all light with wavelength 400nm or lower. This made me wonder, ...
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Is evolution the reason why water is colourless for our eyes?

Liquid water is transparent to most of the visible spectra, whereas it absorbs infrared. Similarly, the air is almost transparent to the visible spectra too. Could these be the reasons why our eyes ...
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Are there any studies on the solar latitude limits of different plant species, beyond which they wouldn't thrive even with suitable weather?

Not sure whether this belongs here or in the Gardening & Landscaping StackExchange, but here goes... According to maps provided in the paper Present and future Köppen-Geiger climate ...
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A poor man's COVID-19 vaccine? [closed]

If person A is infected (COVID-19) and person B is not, could the following work as a vaccination? Person A exhales (coughs?) into a a transparent bag. The bag is radiated for a long time with a ...
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Are mosquitoes attracted to blue lights in particular?

I've been confronting the fact since childhood that mosquitoes are attracted to lights, especially blue lights. Now I know that all insects including mosquitoes are attracted to bright light but I ...
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1answer
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What is the simplest way to demonstrate the germicidal property of UV light?

This is intended for a high school project. I am familiar with the one that studies growth of e coli over time in a petri dish but I a bit concerned about as to how safe a demonstration of this nature ...
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Effect of light intensity on the frequency of stomata

According to this article, the frequency of stomata increases with an increase in the intensity of light. What I inferred from this is, since the rate of photosynthesis increases at higher light ...
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Can UV radiation be safe for the skin?

It is well known that UV radiation can damage the DNA and generally harm our skin. We also know that UV radiation helps on the production of melanin and Vitamin D. From what I could find, the DNA ...
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Do flies avoid infrared light?

If flies avoid IR light, many places can be kept free from flies using IR light. We see insect repellers in many restaurants, but they don't seem to work well. Can IR be a safe & effective ...
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Does cataract condition cause red film when sun is shining?

Since two years ago I have a red film in my field of vision when the sunlight (or a white spot) is at the border (or even lightly behind) of the vision field, the red color is especially obvious at ...
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Killing microorganisms on agar plates?

If I grow microorganisms on agar plates and I expose them to UV light. How exactly will I know that the microorganisms have been killed? I was watching a video that showed spots in the petri dish ...
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Why does a lightsource postpone the time it takes for the leaves falling from a birch tree?

It is autumn and the leaves have already left their trees on all birch and other trees that has leaves, except one. This birch has a spotlight pointed to the tree and it is on 24/7. I have recognized ...
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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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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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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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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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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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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, ...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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
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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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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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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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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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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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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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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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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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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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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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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 ...
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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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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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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 ...