Tagged Questions

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.

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2
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4answers
84 views

Why Light isn't an Acoustic wave?

I just wanted to know why light isn't an Acoustic wave.Is it because light wave doesn't obey acoustic properties?
0
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2answers
45 views

Black Holes and Light [duplicate]

It is said that photons have zero rest mass so how can gravitational force of a black hole affect light? And if photons do have some effective mass while traveling at speed of light then only can a ...
2
votes
2answers
51 views

Why human and most of vertebrates cannot see Near-Infrared light (720nm-1500nm)? [on hold]

On daytime, the surface of Earth is illuminated abundantly by light of spectrum from 250nm-1500nm, that includes near-ultraviolet spectrum (250nm-380nm), visible spectrum (380nm-720nm) and ...
0
votes
1answer
54 views

What is causing the separation of light in this image?

Reflection of keychain LED light on Macbook Pro (2014) screen I have also observed this phenomenon on my mobile phone and on a tablet. I assume this means it is somehow related to backlit ...
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3answers
71 views

Why can we see white objects as white under the sun if the sunlight is yellow?

I get that the sun is producing white light which is scattered threw our atmosphere so that the light of the sun reaching our eyes is yellow. So how come if I look to a piece of white paper under ...
0
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1answer
41 views

Defining photons

I've read every book for my course and all of them describe photons as wave-packets/"bursts" of the EM wave. I just can't appreciate this view of photons. From what I've gathered on photons: Photons ...
-1
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0answers
24 views

On perovskite solar cells [on hold]

Now experiments on perovskite solar cells are in progress . Everybody is looking to improve it's efficiency. One method for improving it's efficiency is by adding multilayers. One key issue in this ...
1
vote
1answer
23 views

Darkest matter on Earth (“pure black”)

What is (for a human's eyes) the natural or synthetical matter on Earth (i.e. not in Space) that emits the least quantity of visible photons while being lightened by sunlight? In this matter, how is ...
0
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0answers
27 views

Why is the color of fire is yellow or blue sometimes? [duplicate]

If you light up any thing it burns in yellow and as well when you light up a gas stove it burns in blue color. What brings this color change?
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0answers
17 views

What instrument can we use to measure light energy released from a light bulb?

Is there any way of measuring the light energy released from an incadescent light bulb without the use of an integrating sphere?
-3
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0answers
58 views

How can Einstein explain particles of light without particles?

how can Einstein explain particles of light without particles? For his Nobel prize he used Newtons explanation except both he and Newton agreed that aether solved the problem of going through holes. ...
0
votes
1answer
39 views

What happens to the energy of photons when two light waves with plane wavefront interferes destructively? [duplicate]

When I began learning about optical interference, I came to know about destructive interference in which light waves cancel each other. How the energy is still conserved ? I found that the ...
4
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3answers
407 views

Why doesn't a ray of light have enough momentum to make us fall?

Why can't light be so powerful that it has enough momentum to make us fall?
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3answers
72 views

Isn't all light polarised?

I apologize if my question does not make sense.(I'm teaching myself microscopy.) So reading Fundamentals of Light Microscopy and electronic imaging by Douglas&Murphy, at one point the author ...
1
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1answer
33 views

Information in twisted light

New Scientist has a story on the use of twisted light to store multiple bits of information per photon. What is this technology, and what are the information density limits per photon? "MOZART and ...
4
votes
1answer
63 views

What common materials absorb most infrared light?

I'm competing in a simple robotics competition where most of the participants use reflected infrared light to detect their opponent. I'd like to make my own robot as difficult to see as possible. What ...
0
votes
0answers
17 views

Raman amplification

Recently I read a bit about Raman amplification. Unfortunately, I did not understand everything. As far as I understood the resulting wavelength only depends on the pumping wavelength. Now I heard on ...
5
votes
5answers
120 views

What exactly are light waves?

We know a sound wave is a disturbance that moves through a medium when particles of the medium set neighboring particles in motion. And using the pressure variations we can plot a pressure/time graph ...
1
vote
1answer
42 views

Why does projecting black light from a screen mask white light shining through it?

I had a Macbook Pro, and remember being intrigued when I noticed that the apple logo on the back of the screen allowed sunlight to shine through in an Apple shape on the front of the screen when ...
2
votes
0answers
29 views

Is there such a thing as purple light? [duplicate]

This is a question as much about color perception as the physics of light. Since I have normal vision, without color blindness, I will draw on my experiences in formulating my question. I will add ...
2
votes
1answer
65 views

Can a single technology be used to observe light at any wavelength?

Radio waves are observed using induction in antenna. Visible light is observed exploiting electronic transition in matter. Is it possible to do the opposite? If not why?
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2answers
85 views

Can you see back in time? [closed]

When you look at the stars, the light that you see is probably hundreds of years old. Which means that you don't know if they still exist. Does all this mean, that if you fly in a speed faster than ...
4
votes
1answer
61 views

Experimental determination of speed of light

How is the speed of light measured by the most current method i.e. using lasers and atomic clocks? Alternatively, is there a better method?
0
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1answer
41 views

Beam of electromagnetic wave, with radius of 3cm or less

I need to create a beam of electromagnetic wave, with radius of 3cm or less, for distance about few meters. What is the minimum frequency (maximum wavelength) that it is really possible?
1
vote
2answers
82 views

Can we get the refractive index of a prism by using white light?

Can we get the refractive index of a prism by using white light ? I guess since white light is non chromatic, it is not possible.
5
votes
4answers
560 views

Why is an opaque body opaque?

When does a body qualify to be called an opaque body? Is it anybody which cannot let visible light through it or is there any other definition? And when and how does a body allow radiations through ...
0
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5answers
75 views

Is anything coloured “infra-red”?

All our day-to-day objects are things we can see, and thus we can conclude that their colour lies in the visual spectrum. Is there matter that does not have a colour within the visual spectrum? What ...
2
votes
2answers
50 views

What exactly is color? [duplicate]

What is color? “The property possessed by an object of producing different sensations on the eye as a result of the way the object reflects or emits light”…. You might say. So take a white object ...
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votes
0answers
17 views

Quantum camera using euclidean rotation and kabbalah

I've been playing around with procedurally generated images and the kabbalah/tesseract the last few weeks. Imagine a 3D cube sitting on top of a 2D colour wheel. One thing I noticed is that 3D ...
38
votes
6answers
5k views

Is there a physical reason for colors to be located in a very narrow band of the EM spectrum?

The portion of the electromagnetic spectrum that is visible to humans are wavelengths between 380 and 750 nanometers. I am aware that animals have different capacities than humans, but the EM ...
3
votes
2answers
43 views

Whats the reaction that creates light when I open BreatheRight strips? [duplicate]

Darken a room. Pull open the sides of a BreatheRight nose strip (they work for me, though may be placebo effect). Notice the blue light coming from the separating adhesive.
2
votes
3answers
302 views

If I turn the light off in a room why does the light instantly disappear? [duplicate]

So today I was asked a question which I found very simple yet I honestly couldn't explain (embarrassingly). One of my mum's friends who knows I'm a scientist asked me "If I turn the light off in a ...
0
votes
1answer
46 views

Path Difference Due to Angled Incident Light

If light incident on a diffraction grating makes an angle $\alpha$ with respect to the normal to the grating, show how $$m \lambda = d\sin\theta$$ becomes $$m\lambda = d[\sin(\theta - \alpha) + ...
3
votes
3answers
189 views

Making a plastic scintillator glow?

I have a plastic scintillator I had purchased off eBay, which is believed to be BC408 http://www.phys.ufl.edu/courses/phy4803L/group_I/muon/bicron_bc400-416.pdf Upon shining a small UV LED (10-40mA, ...
0
votes
1answer
41 views

How does Huygens Principle explain interference?

How exactly does Huygens theory about the propagation of wavefronts account for interference?
2
votes
2answers
51 views

Negative frequency contributions for very short pulses?

I am wondering if very short optical light pulses can have a Gaussian envelope? When I describe the pulse shape with a Gaussian than the frequency distribution has also a Gaussian shape. But if the ...
5
votes
3answers
1k views

What does the colour of a light bulb depend on?

There are light bulbs of different colors available (red, green, yellow, white, etc). What does the color depend on? Is it on the temperature of the filament?
1
vote
4answers
320 views

What's so special about the speed of light? [duplicate]

What's so special about the speed of light? Why do many equations in physics include the speed of light in vacuum $c$? Why do so many thing depend upon it? Why can't it be the speed of sound? ...
2
votes
2answers
94 views

Where's all the light going in the universe?

According to my knowledge, matter can not go faster than light, and light is emitted constantly in the universe from many types of reactions. If this is so, then isn't light constantly getting past ...
1
vote
1answer
61 views

Splitting a light wave

What I want to ask is what would happen if you split a single light ray (a photon) into two using a half silvered mirror? Would the emerging light rays have half the amplitude as the original one or ...
2
votes
2answers
91 views

Why does light fade from a room?

So basically in my toilet I have this really bright ceiling light, but when I turn it off it doesn't just instantly plunge me into darkness, but rather sort of fades out over a few seconds. It looks ...
1
vote
3answers
109 views

What conditions should be met to notice a Doppler effect on light?

What relativistic conditions should an observer meet to notice the Doppler effect on a sample light wave, and is it even possible for one?
-4
votes
1answer
52 views

is it possible to extract spectrum (color in general) from an animal [closed]

if i may ask....can this be ASAP? :3 my problem: okay this is going to sound lame, but i was wondering if it is possible to extract color (specifically spectrum) from an animal. this question ...
3
votes
1answer
35 views

Is it possible to improve the efficacy of light bulbs with a semipermeable mirror? (The greenhouse bulb)

Let us imagine that there exists a material that reflects infrared radiation, but is transparent for visible light. Could we take an incandescent bulb and add this material to the inner surface of the ...
1
vote
1answer
41 views

Pattern on mesh office chair emulates thin film interference for curved surface. Possible to form an equation?

I saw a chair that looked like this at the dentists office yesterday, and the pattern caught my interest, as the light patterns emulated thin film interference fringes formed by an object that has a ...
0
votes
1answer
37 views

AC wire radiation

I'm trying to test my recently installed MEEP program for a very simple AC current. I know that for DC current, Ampere's law dictates that the magnetic fields must drop off as 1/r. How does this ...
8
votes
2answers
1k views

Would using Cherenkov radiation for lighting be feasible?

Could Cherenkov radiation be used for general illumination, for example, to replace LEDs, light bulbs etc? I.e. are there, or could there be, methods to produce substantial amount visible light with ...
1
vote
1answer
69 views

Why seeing further in “timespace” does not add up?

I've read that astronomers have received a light (a photon) 13 billion years old. Here's my question: If we start to turn the clock backwards all matter, energy, etc should start heading to the ...
1
vote
1answer
41 views

One way mirrored hollow sphere [closed]

Imagine a one way mirror, where from one side it appears to be glass, but from the other side, it appears to be a mirror. Now, fold that sheet into a hollow sphere, so the inside is mirror (and I'm ...
4
votes
2answers
174 views

Is manufacturing roughness really the only reason we don't see optical interference in thick dielectrics like windows?

I had always kind of wondered why we didn't see interference in things like windows -- we were taught that the condition is that the thickness of the film/slab/medium just has to be an integral number ...