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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63 views

How to demonstrate total internal reflection?

How can we demonstrate total internal reflection practically to explain it clearly?
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3answers
55 views

Does a high energy photon experience deceleration or direction-change when it impinge into water or something due to the change of refraction index?

Wave experiences refraction when it propagates into another medium which has different refraction index. Lights surely does experience refraction at the border of mediums which have different ...
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7answers
918 views

Why can't we have a wave of particles?

I understand the nature of light can be complex and has extensive theories/experimental data. We hear light can be both a wave and particle, so why can't it be both, a wave of particles?
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3answers
95 views

Does light color change when refracting? [duplicate]

When light refracts from a medium to a second one, its frequency stays the same, and its wavelength changes. If this is true, why we see the refracted light ray's colour is the same as the incident ...
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0answers
10 views

Dangerous levels of ozone from combined UVB lamps?

I have a reptil UVB lamp in my room, and a de-humidifier that uses a UV lamp to clean the air passing through it. Honestly since I got it working (the lamp was dead at first) my room is mold free. I ...
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0answers
33 views

How do cathode ray tubes (CRT) synthesize colours?

I just read about how LCD displays were based only on black&white contrasts, and only colour filters on each subpixel generated the colour of a pixel. However, how does that happen for a CRT? Is ...
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2answers
42 views

Is every ordinary coloured transparent paper an optical filter?

Can any red coloured transparent paper be used as an optical filter that only allows red colours through it?
2
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1answer
125 views

Red color has largest wavelenght and violet minimum (in the range of visible light). then why does violet light appears reddish? RED + BLUE = VIOLET [duplicate]

My question is simple. Green light is more similar to red light than violet, then why is violet reddish and green not? in the language of frequencies and wavelengths, red and violet should contrast ...
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0answers
41 views

Dispersion in a rectangular prism

Why are the colours visible only at the fringes of the light refracted through a rectangular prism?
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0answers
25 views

What is the perceived color of a D-illuminant?

I am implementing a software that simulates the color of the sky. To do this, I use a model that takes as input the sun position and returns the Yxy components of a D-illuminant for each point of the ...
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1answer
52 views

Human and Ultraviolet light

As I know, ultraviolet light can be created from burning something at high temperature. So I have a question: Can a human body become a source of ultraviolet light at high temperature? If the answer ...
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1answer
426 views

Refractive Index formula for denser to rarer medium

I learnt that the formula for refractive index when light travels from rarer to denser medium is (sin i / sin r) where i = angle of incidence r = angle of refraction Is the same formula used for ...
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2answers
115 views

A black torch to darken everything

Can we ever have a black colored (the color of the light and not the body's color) torch that darken (or dis-illuminates) everything? While compared to a normal torch it would function in an opposite ...
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0answers
71 views

Need to use lasers,mirrors and prisms for a project.How to make the light visible and presentable at the same time? [closed]

Alright so I really want to put some art into science for my project.project. I'm thinking of creating a beautiful image,preferably in air.I read about the visible lime-green lasers but i still want ...
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2answers
694 views

Is turquoise closer to blue or green?

I am having a discussion with my coworkers. Does anyone know what is the wavelength of turquoise color and whether it is closer to green or blue when comparing their wavelengths ?
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1answer
146 views

Why do some sunsets have a green flash?

Some sunsets exhibit a phenomenon called "green flash," where there is a quick flash of green light right as the sun is setting. I have seen this myself several times, and sort of understand it. I am ...
2
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2answers
42 views

Modelling radiance profile of a light bulb

For Graphics I need to model the shape and the radiance profile of an existing light bulb in order to use it in a ray-tracing application. I can freely choose the light bulb. The strategy must not be ...
1
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1answer
54 views

Confused about length contraction and aberration [duplicate]

Einstein states that a moving object's shape changes due to the length contraction. But people had done such an experiment: Taking photos to a moving object, but they didn't find Lorentz contraction, ...
2
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0answers
90 views

Why do particular materials allow particular light waves to pass through them? [duplicate]

To be honest, I really don't understand this at all. If we take cardboard for example, obviously gamma rays can penetrate cardboard because the light has such a high energy, and obviously radio waves ...
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0answers
68 views

Optical Simulation Tool [duplicate]

I am a student and trying to design an aperture from which a light will pass will project on a sensor. I tried to find some software simulation tool for this purpose where i can draw the aperture ...
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1answer
28 views

Relationship between diffused light and intensity

I was wondering if the relationship of the intensity of diffused light is a linear correlation to the diffusing material. Basically will the intensity of the diffused light change in a linear fashion ...
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4answers
120 views

How do we demonstrate that all spectral colors exist in nature?

Spectral emission by elements occurs in discrete wavelengths. There are only about 118 elements. My question is whether there are pure colors either disfavored in nature or even disallowed? The sun ...
2
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0answers
40 views

Is TRUE invisibility possible?

First off, this question may seem highly stupid at first, but it arose from past cartoon memories. In the cartoon Tom & Jerry from the 1940s, there was already hypothesizing over cream that, when ...
5
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2answers
130 views

Would there be fringe pattern in this arrangement?

Figure shows a standard two slit arrangement with slits S1, S2. P1, P2 are the two minima points on either side of P. At P2 on the screen, there is a hole and behind P2 is a second 2- slit arrangement ...
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1answer
66 views

Does putting color filters make the sources incoherent?

In Young's double slit experiment a single source is used to illuminate two slits which then acts as two coherent sources to produce interference pattern. But, what if I put color filters on the two ...
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2answers
80 views

Does any material glow, under appropriate conditions?

Given a high enough temperature, or a high enough electrical field, can we make every material emit visible light?
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1answer
815 views

Glass that only allows light of specific amplitude to pass through it

Is there a type of glass, mirror or lens that allows only lights of amplitude equal to or greater than a fixed value to pass/reflect through them?
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2answers
166 views

Why does welding produce UV light?

Looking directly at a welder is dangerous because large amounts of UV light is produced. What makes this light? Is it electrons from the current that excites metal atoms, and these atoms sends out UV ...
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3answers
4k views

Is it possible to avoid the radiation that caused the American flag turned into white on the Moon? [closed]

While lunar images have proven that the American flags planted during the Apollo missions are still standing on the moon, lunar scientists have now said that they probably no longer hold the iconic ...
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1answer
61 views

Why are radio waves in the 1.43 - 2.5 Mhz range invisible?

Visible light diapason is 400 - 700 nm which is 1.43 - 2.5 Mhz. If using an antenna I would broadcast steady sinusoidal wave in this range, why the EM emitted by the antenna are not visible? Suppose ...
4
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4answers
196 views

What will be the relative speed of a photon in a light ray to another photon of opposite direction light ray?

If two light rays start simultaneously in the space from exactly opposite ends in opposite direction that is separated by a distance of 600000 km in a way they meet at the mid point (300000 km from ...
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1answer
106 views

What really is reflection? [duplicate]

What really is reflection? Is it just the reemission of EMR? I asked my teacher, he said in quantum sense, it is true. But when I read something about emissivity in Stefan Boltzmann's equation, it ...
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3answers
102 views

Intuitive understanding of wavelength

Light is described as having wavelength. I can somewhat understand this in connection with for example the double slit experiment, that photons interact spatially in a wave like manner. But can the ...
4
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0answers
67 views

Optical Bloch Oscillation

I have a doubt about how the optical Bloch oscillations happen in a 1D photonic crystal. I try to explain: in a photonic crystal with discrete translational symmetry in one direction I superimpose a ...
3
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1answer
85 views

Why are reflected objects blurry?

While this may seems like a strange question, I'll try to explain it the best I can. Like 75% of Americans, I wear glasses and contacts to correct my worsening vision. I'm not far sighted so objects ...
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2answers
70 views

2 torches with the same power - More lumen?

I didn't find an answer for this. A friend and me argued about the brightness-impact of multiple bulbs/torches. I told him, that 2 torches with the same power (the same amount of lumen and ...
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2answers
58 views

Can you replace the backlight of a thin film transistor (TFT) with a mirror?

I basically know how TFT' displays work. They have on both sides a polarizing foil, in 90 degrees with the crystals in the middle modifying which light particles should pass through or not. The light ...
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1answer
92 views

Why isn't steam/cloud blue like liquid and solid water?

Most of us here are aware as I think that pure water has a natural quest to absorb visible red colour wavelength slightly due do which liquid water and sometimes even ice appears to have a blue colour ...
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2answers
726 views

what is the best way to collimate light emitted by a led?

I'm new to this forum. This is half a question, half a challenge. And it's more engineering then physics but I thought I might get good insights from a physics forum. I would like to cure a UV ...
2
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1answer
47 views

“backwards” Diffraction Grating with light source at maxima (1st, 2nd, nth order)?

How will a light source with a specific $\lambda$ positioned right at the nth order maximum pointing towards a diffraction grating be affected? Will it come out "directed"?
3
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3answers
137 views

'ting' 'ting' sound from a tube-light?

Whenever I light up a tube-light it makes 'ting' 'ting' sound every-time it blinks. I am talking about this tube-light Why is it so? I think its because of sparking(inside glass tube) ...
2
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2answers
67 views

Can we see refraction of light in the air with our eyes?

Can we see refraction of light in the air with our eyes? I am asking that because every night I see that the light in the street moving little is that because of change in the air? I do not mean ...
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1answer
108 views

Can a wave exist on the “face” of a wave?

It would seem that this would be possible with waves in water. What about other waves Clarification: Given a wave starting from a point of impact, in water, at: Time 0:00 and xyz 0,0,0 and the ...
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4answers
79 views

Is 'color' characteristics of a body or characteristics of light?

In situation when body exposed by light, is 'color' characteristics of a body or characteristics of light? Is there any difference on macro/micro levels? Will exist such term as 'color' in parallel ...
2
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0answers
115 views

If photons don't have mass, how can they accelerate objects? [duplicate]

As far as I know photons don't have mass but they do have momentum ($p=mv$). Scientists say that if we put a shiny (reflective) shield of large radius in the vacuum of space, then light from sun will ...
2
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1answer
57 views

Speed of different em radiation in a medium

Does all frequency of light travel with the same speed in a particular material like glass? Since by cauchy's relation refractive index change with wavelength which implies the speed also changes. ...
3
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1answer
122 views

Why does the Sun turn red near sunset?

At daytime the Sun's light is yellowish if not near white. Why when the Sun starts to go down that it's light turn more red. I don't think the earth's rotation is so rapid to cause a red shift. Why ...
16
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4answers
1k views

Why can't single LEDs produce white light directly?

Why does production of white light using a LED require combining a short wavelength LED such as blue or UV, and a yellow phosphor coating? Why can't a single LED produce pure white light?
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2answers
685 views

Why does mixing every paint colour produce gray instead of white?

I'm trying to reconcile these facts, If I had paints of the primary colours and I mixed them together, I would produce gray. White light contains every colour. My most convincing attempt to ...
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1answer
53 views

Does fluorescence produce most of the colors we see day-to-day?

I read the following on Wikipedia regarding fluorescence, Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation... The most striking ...