Questions tagged [light]

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

Filter by
Sorted by
Tagged with
0 votes
1 answer
54 views

Image sensitivity of eyes and peripheral vision

I have bad eyes and need glasses. However I have noticed when it is dark, I am able to see contrasting colours a lot better in the corner of my eyes, than in the center, e.g a mark on my wall I can't ...
user avatar
5 votes
1 answer
111 views

How many photons does a GFP molecule absorb per second?

I'm trying to calculate how many photons will a GFP emit per second. The calculation seem easy just multiply the number of absorbed photons by the quantum yield. But how can I obtain the number of ...
user avatar
  • 478
7 votes
1 answer
392 views

Do color-blind people have more rod cells in their retinae than the normally sighted?

All types of color-blindness are said to be caused by the defect or lack of cone cells in the eyes[1]. Since cone cells sense color[2] and rod cells can only sense light intensity[3], the lack of cone ...
user avatar
  • 513
6 votes
1 answer
131 views

How is the extraordinary eyesight of some deep-sea creatures explained?

Mantis shrimp is a marine crustacean that is known to have a vision system that is much more complex than the eyes of many animals living on the ground. As explained here, it has 12 types of ...
user avatar
  • 161
1 vote
0 answers
45 views

What is the true response of human photoreceptors to different wavelengths? Why is there so much disagreement in the literature?

I can find several qualitatively different diagrams of the responsiveness of human cones and rods to different wavelengths of light. A page referencing Bowmaker and Dartnall, 1980 has the following ...
user avatar
0 votes
0 answers
42 views

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 ...
user avatar
0 votes
2 answers
86 views

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 ...
user avatar
  • 11
-1 votes
3 answers
347 views

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 ...
user avatar
  • 131
0 votes
1 answer
83 views

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 ...
user avatar
2 votes
1 answer
87 views

Why when measuring turbidity do we use the minimum wavelength?

As a preface, I read a few other related posts and was able to gather some knowledge, though without any background in physics I am having some trouble here piecing together a coherent view. I looked ...
user avatar
2 votes
0 answers
13 views

Most optically transparent muscle phantom?

I am trying to use Schlieren imaging techniques to visualize how a sound wave propagates through muscle tissue. In the past, when needing to experiment with muscle we would use an agar based muscle ...
user avatar
  • 133
-3 votes
2 answers
78 views

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 "...
user avatar
-2 votes
1 answer
71 views

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 ...
user avatar
1 vote
2 answers
332 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, ...
user avatar
  • 975
1 vote
0 answers
48 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 ...
user avatar
2 votes
0 answers
21 views

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 ...
user avatar
2 votes
1 answer
148 views

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 ...
user avatar
  • 137
1 vote
1 answer
302 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 ...
user avatar
  • 11
1 vote
1 answer
49 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 ...
user avatar
5 votes
1 answer
341 views

What happens to plants if they are exposed to "sunlight" 24h a day?

I just wondered if one could grow plants faster, if they were exposed to sunlight-like light all the time. In a similar question which is not the same, I could confirm that plants have different ...
user avatar
  • 1,501
0 votes
1 answer
95 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 ...
user avatar
  • 392
14 votes
2 answers
2k views

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 ...
user avatar
  • 315
0 votes
0 answers
195 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 ...
user avatar
0 votes
0 answers
35 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 ...
user avatar
1 vote
1 answer
177 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 ...
user avatar
2 votes
1 answer
56 views

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 ...
user avatar
  • 23
1 vote
2 answers
584 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, ...
user avatar
  • 375
3 votes
0 answers
103 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 ...
user avatar
  • 59
2 votes
0 answers
62 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 ...
user avatar
0 votes
1 answer
40 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, ...
user avatar
  • 223
1 vote
1 answer
98 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 ...
user avatar
0 votes
0 answers
37 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, ...
user avatar
  • 917
2 votes
1 answer
401 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 ...
user avatar
  • 171
1 vote
0 answers
539 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 ...
user avatar
  • 105
3 votes
0 answers
86 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 ...
user avatar
2 votes
0 answers
33 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 ...
user avatar
0 votes
2 answers
124 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 ...
user avatar
  • 462
5 votes
2 answers
2k 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 ...
user avatar
2 votes
0 answers
72 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 ...
user avatar
1 vote
2 answers
111 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 ...
user avatar
1 vote
0 answers
29 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?
user avatar
  • 464
1 vote
3 answers
11k 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 ...
user avatar
  • 257
0 votes
1 answer
61 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 ...
user avatar
7 votes
1 answer
265 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 ...
user avatar
0 votes
0 answers
119 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 ...
user avatar
2 votes
0 answers
2k 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 ...
user avatar
8 votes
2 answers
350 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". ...
user avatar
1 vote
1 answer
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? ...
user avatar
1 vote
1 answer
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 ...
user avatar
2 votes
0 answers
85 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 ...
user avatar