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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Radiance increase via two sources [closed]

Can two sources of white light shined at the same general location increase the resulting rasiance?
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1answer
26 views

Dynamic equations for propagation of light through dust

For smoothly inhomogeneous media light propagation can be modeled by Maxwell's equations with non-constant $\varepsilon$ and $\mu$. This allows to relatively easily model propagation in the medium ...
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1answer
57 views

Physical effects on light from stars

I was thinking about how we see stars at a distance, the light that travels from them is affected by the Earths atmosphere, gravitational lensing and dust etc., but there doesn't appear any equation ...
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1answer
54 views

Can we get a true negative of an image reversing the spectrum?

In photography the negative means the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest. But I was wondering: is this the way how negative should ...
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1answer
68 views

Bending light (photons) into an orbit

I was wondering and researching about light bending and reflection - I'm wondering if its possible to bend a light beam into a loop (orbit)? I know that light can be bent and reflected (even 100% ...
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9answers
5k views

How would night sky look like if the speed of light was infinite?

Would it be brighter? Different color? Gravitational lensing? Would black holes exist?
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4answers
174 views

Space orientation of light waves

Recently I've started to be really intrigued with the electromagnetic spectrum and bumped into this problem: According to the wave theory of light (or any electromagnetic wave, really), the magnetic ...
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10answers
851 views

How far can light go?

When a ray of light is projected, (say) from the surface of Earth to outside in space. The condition is that, there is no obstruction to it till infinity (it travels only in vaccum). My question is ...
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2answers
185 views

Plane polarized light?

I have heard about plane polarized light: light wave which has vibration in one plane. My curiosity forces me to ask a doubt, is there any way to produce polarized light wave which has vibrations in ...
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0answers
27 views

What property of medium is directly related to light propagation speed in that medium? [duplicate]

Refractive index is used to calculate phase velocity of light in medium, other than vacuum. Recently I had a discussion with somebody claiming that light is slower due to magnetic field of atoms. I ...
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2answers
136 views

Is there a relation between music chords and visible light palette [closed]

Ok I have no idea if this is the right stackexchange so if you know who would know please tell me :) In music there are groups of notes that, when played togheter, are basis to harmony. Since both ...
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0answers
54 views

Diffraction of a thin mirror

I have a question about a particular case of light diffraction. A laser light collides into a "hairline" mirror (I mean a straight line mirror that halves the wavelength dimension), see the image ...
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4answers
45 views

Is there some difference between blue light and light covered by blue paper?

Let´s talk only about photons absorbed by detector. Would it detect something else if the photons came from blue star than if the photons were filtered by blue paper? And what about ultraviolet ...
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3answers
110 views

Why does the light reflecting off of ocean water sometimes appear 'smoother'?

Looking out the window at some water in the Harbour - I noticed that some parts of the water appear 'smoother' than others. My question is: Why does the light reflecting off of ocean water ...
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2answers
93 views

Penny dropped in the water: What would you see if transmitted light is parallel to the incident surface

I'm working on a problem which asks what is the greatest diameter of a paper you can use to totally shield a penny dropped in the water from view. The question claims that if the transmitted ...
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0answers
86 views

Why can't we see Rainbows from its end points? [duplicate]

We see Rainbows many times, but we always see them Horizontally or from Sideways. Why can't we see it from under it?/From the point where it starts or ends(end points)? I also want to stress on that, ...
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1answer
95 views

Can unpolarized light be created from polarized light?

I have a question regarding this topic. According Stokes Parameters theory, unpolarized light could be described as a superposition of two independent beams of equal intensity and orthogonal ...
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0answers
23 views

Does dispersion take place in our eyes? [duplicate]

What do we see if a single ray of white light falls in to our eyes ? Doesn't it undergo dispersion ?
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1answer
162 views

Is it possible to project black light? [duplicate]

A thought passed by me and I wondered if projecting black light was possible. We can make lights with many other colors, but I'm not so sure about black. So, is it possible? Has it been done?
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5answers
162 views

Why is microwave better than visible light for point to point data communication?

In the electromagnetic spectrum, it appears that the shorter the wave length, the better the bandwidth due to higher frequency. Some communication systems utilize microwave to transmit data to offer ...
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1answer
1k views

Effect of varying distance of light source from a Light Dependant Resistor

I'm doing the experiment described here and I have a few questions about it. I have a miniature light dependent resistor (LDR) hooked to a multimeter set to $\Omega $ and a $25\,\mathrm W$ Light ...
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2answers
76 views

Why doesn't the color of an object change when signal of different frequency impinge upon it?

Correct me if I'm wrong but I've always thought that the color that an object has is due to the oscillation of the atoms that makes up the material of that object. When white light is shine upon an ...
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3answers
2k views

What do we see while watching light? Waves or particles?

I'm trying to understand quantum physics. I'm pretty familiar with it but I can't decide what counts as observing to cause particle behave (at least when it's about lights). So the question is what do ...
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4answers
178 views

Why Light isn't like 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?
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2answers
87 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 ...
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2answers
677 views

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

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 ...
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1answer
78 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
346 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 ...
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1answer
52 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 ...
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1answer
97 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 ...
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0answers
113 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
58 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?
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1answer
158 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 ...
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3answers
466 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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5answers
274 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 ...
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1answer
93 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 ...
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1answer
5k 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 ...
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0answers
26 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 ...
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5answers
340 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 ...
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2answers
152 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 ...
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0answers
327 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
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3answers
120 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
114 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
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1answer
73 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?
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1answer
46 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?
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2answers
374 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.
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4answers
1k 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 ...
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5answers
87 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 ...
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2answers
91 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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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 ...