Questions tagged [light]

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

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82 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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132 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 ...
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633 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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Surface Power Density of Fluorescing Reaction

I am looking to find out what is the ballpark power density of a fluorescing PCR reaction using a SYBR Green or Taq Man dye might be. Is it on the order of $E_e=1mW/cm^2$, less or more? Any help of ...
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Dawn simulation - does color change affect waking up?

just curious. Are there any works or research results related to the influence of light color used for dawn simulation? I mean those wake-up lights which try to simulate dawn to make waking up better ...
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1answer
133 views

Do non-green flower colors have any functional interactions with the sun?

I always hear the pseudo-evolutionary claim "plants are green because they need to use red and blue light". If this premise to my question is true, What (if any) other functional relationship occur ...
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1answer
4k 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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1answer
1k views

Is it safe to look indirectly at the Sun?

I.e., is exposure of sunlight onto the peripheral vision less damaging than exposure onto the fovea?
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189 views

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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1answer
167 views

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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489 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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93 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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99 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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1answer
146 views

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
48 views

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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1answer
2k views

Why insects are attracted towards light? [duplicate]

Many insects like bees, dragonflies, wasps and other small insects are attracted towards light. Sometimes they are in groups, sometimes they are in solitude. When the light source source is switched ...
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45 views

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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499 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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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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1answer
2k 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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469 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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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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3k 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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52 views

What are the effects of non-ultraviolet light radiation on DNA?

I am trying better understand the effects of varying the frequency of light on DNA, however, most of what comes up is "UV light" and how it is damaging to DNA (presumably by ionization). Have there ...
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How do PER/CRY complexes accumulate in the cytoplasm?

The Period/Cryptochrome (PER/CRY) complex is a heterodimer that transcriptionally regulates circadian rhythm. When it is phosphorylated, it is transported to the nucleus and it inhibits a ...
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Would blue light be effective to help average people when sunsets come much earlier in the day?

I know people with SAD (Seasonal Affective Disorder) benefit from blue light in the winter as night-time comes much earlier (in the UK, sunset is around 4pm in December, compared to 9pm in June). ...
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3answers
10k 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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Would green light look different if blue and red cones were deactivated

When looking at a graph plotting "blue", "green" and "red" cones reponses to different wavelengths, you can see that any wavelength trigerring a response from green cones ...
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372 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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109 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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1answer
57 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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21k 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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1answer
91 views

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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1answer
45 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 ...
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1answer
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Fluorescent purple flowers?

Do some flowers fluoresce? Some deep purple Lobelias and larkspurs seem to glow and confuse my eyes in sunlight. It reminds me of those blue LED Christmas lights (they come in strings with other ...
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1answer
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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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112 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
759 views

What happens to H+ when Glycerate 3-Phosphate is converted to Triose Phosphate?

The conversion from Glycerate 3-Phosphate to Triose Phosphate requires: $ATP \rightarrow ADP + P_i$ $NADPH \rightarrow NADP + H^+$ So what happens to the $H^+$? Is it in-effect "recycled" back to ...
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Why isolated chlorophyl emits red light?

If we observe isolated chlorophyl solution with UV light, chlorophyl is seen as red. explanation suggests that when specific atom of chlorophyl absorbs UV light, atom gets excited and in a short time ...
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157 views

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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34 views

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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36 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, ...
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117 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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1answer
102 views

Cells scatter light in solution. Do they refract?

For part of an exam question, "why do cells grown in liquid cause turbidity?" I answered that cells refract light. The correct answer was that cells scatter light. Isn't the light scattering ...
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Can insects be killed by intense visible light?

Some mosquitoes and flies were sitting on the white ceiling. I took a very powerful flashlight to try and daze and then vacuum them. When I put the flashlight's head against the ceiling (with a ...
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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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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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