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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Why does a blue book appear black in red monochromatic light?

Why does a blue book appear black in red monochromatic light? I found the question on this website but it doesn't provide an explanation.
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2answers
60 views

Why haven't we created a material that is completely invisible to the human eye? [closed]

From what I understand, If something was not reflecting photons in any direction, you could then see through it. If photons transfer into thermal energy could something very cold help? Could the ...
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0answers
36 views

Firing Single Photon [closed]

We know (or pretend to know) what will happen if we fire one photon at a time and let it pass through slit/slits. But what if we don't use slit/slits and fire photons one at a time at a screen? What ...
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0answers
23 views

Clarification regarding atmospheric opacity

I have taken a look at the related questions Can someone explain to me the concept of atmosphere opacity? and Why can spacecraft observe terrestrial gamma rays, but terrestrial observers not ...
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3answers
107 views

Why must $v$ be $< c$ in the Lorentz transformations? Do these equations not apply to light? [duplicate]

I was trying to understand how things look from the perspective of light. Looking at the Lorentz transformations, it seems that the universe would contract along the direction of movement into a plane,...
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0answers
56 views

How was microscope-level zoom created by a lens and a water droplet?

It was a rainy night. My glasses were speckled with fresh water droplets. I looked at a distant street light and I was surprised to see cells - a single cell was zoomed in to the level where I could ...
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1answer
51 views

Can light change the shape of a black hole?

If light orbits a black hole without ever getting closer or further from it, and the black hole pulls on the light from all directions nearly simultaneously, does the black hole extend at its equator? ...
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1answer
18 views

fiber optic face plate physics-opaque to transparent behavior based on distance of object?

Please look at this video below. its of fiber optic plate or compressed fiber lens Here it seems that the object- which is the book or letters here, is visible only when the plate is touching the ...
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1answer
28 views

Why anti-reflective coating of silicon nitride colour varies with thickness?

Why the silicon nitride colour varies with the thickness?
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0answers
35 views

What properties would a laser need to have in order to be visible in plain air?

We all know what happens if you use a laser pointer in foggy/dusty conditions: you can clearly see the line from the source to the destination. However, in plain air it is not. My question is, what ...
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0answers
29 views

Can refraction be thought of as a special type of reflection?

So, I know the difference between refraction and reflection but I've been wondering today if maybe refraction could be thought of as a special type of reflection with a very obtuse angle. Reflection ...
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0answers
58 views

Path of photon from Sun to earth unaltered? [duplicate]

I got into a discussion regarding the light from the Sun that reaches the Earth and whether it maintains the same path from the moment it was emitted to the point it is processed by our eyes. My ...
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4answers
5k views

Why does the sun have to be nearly fully covered to notice any darkening in an eclipse?

I was looking at eclipse footage and I noticed that it doesn't get any noticeably darker until the very end when it suddenly all the light is gone. As the moon blocks out the Sun, I would expect that ...
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1answer
60 views

How does the levitating water illusion work?

After watching a movie in which levitating water was used as an illusion, I was curious to discover how it works. Unfortunately I cannot find any great explanations of the science behind the effect, ...
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1answer
43 views

How come we can get mirror-like effects from dark surfaces?

Question: If I understand correctly, an object's color is determined by the optical frequency which it does not absorb. So an apple appears red because it only reflects red. My question is, if this is ...
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0answers
33 views

Cheap DIY Zernike-Phasecontrast: Optical Thickness of a inkjet/laser printed contour for phasering? [closed]

Rough guess: Optical Thickness of a inkjet/laser printed contour? Edit I was wondering if there is any research regarding the refractive index and the height of an inkjet or laser printed contour?  ...
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1answer
70 views

Doesn't the doppler effect prove that light is a wave? [closed]

According to me doppler effect can only be applied to waves and not particles, as we apply doppler effect on light it proves it having wave nature and not particle nature.
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1answer
22 views

Reason for absorbance

First quoting the example which raised my curiosity"when light passes through polaroid it absorbs certain direction light rays" My question is how this phenomenon of absorbance occurs is this some ...
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0answers
9 views

What is the relation between color perception and the lux of white light to which it is exposed?

If we have a particular shade of blue in 100 lux of white light, how will the perceived shade of blue change if the illuminance of white light is increased to, say, 200 lux? or 500 lux? I want to know ...
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2answers
88 views

Does every past state of the Earth currently “travel” through the universe?

So I just read this question. The 27 year old user asks if it would be possible to see his own birth if he would be 27 lightyears away from the earth and the answer states ...
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2answers
962 views

What is the color of a group of trillions of electrons, protons, and neutrons

Since an electron is smaller than visible light, then what what color would a group of electrons (trillions of electrons) be if there were enough of them to be seen by the eye? What color would a ...
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2answers
973 views

Is it possible to have solid light? [closed]

Is it possible to have solid light? If so, what would it be like?
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1answer
29 views

What causes the bright glow on the edge of fiber optics and translucent sheets?

http://imgur.com/8PHxy6z On top of the picture, we have a number of translucent sheets. The edge of the sheets seems to glow compared to the rest of the body; why is this? On the bottom of the ...
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2answers
101 views

Why doesn't sunlight ALWAYS get split (into monochromatic) when going through the clouds?

It is my understanding that clouds are largely made up of water, which is known to split white light into its frequency components, and that's why we see rainbows sometimes. My question is, with ...
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2answers
2k views

What is the farthest planetary body or star system object we have observed using visual light?

What is the farthest object which we can get a direct Detailed visual image of using visible light which appears more than just a dot and falls into one of the following categories: Planet Satellite ...
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0answers
37 views

Why does violet (purple) color contain red component? [duplicate]

We see rainbow color on short-wavelength side as violet or purple: And this color is obviously contain R component from RGB. How can this happen, if only blue pines can percept this color, while ...
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1answer
46 views

Proving that angle of incidence over angle of reflection is constant in Snell's Law

First let me state what I think I know: Snell's Law states that $\frac{sin(i)}{sin(r)} = \frac{v_1}{v_2}= \frac{\lambda_1}{\lambda_2}= \frac{n_2}{n_1}$ where i is the angle of incidense and r is the ...
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0answers
32 views

Self propagating EM waves mechanism of propagation

Electric fields generate magnetic fields and visa/versa,and this is attributed to be how a light ray self propagates. Can anyone further clarify how exactly light rays self propagate? If the mechanism ...
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2answers
75 views

The criteria of light

My question is regarding if the "speed of light" 299,792,458 m/s should only apply to certain frequencies of light/colors/amplitude and most the medium in which it travels at 299,792,458 m/s . Shouldn'...
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5answers
458 views

What is the difference between heat and light?

What i know is that light is an electromagnetic wave. Is heat also an electromagnetic wave of certain wavelength other than light ? Why the light wave cause heat in an object when it falls on the ...
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2answers
47 views

How can you easily measure your visual range? [closed]

There are numerous ways of estimating your hearing range by generating sine waves at a certain amplitude and trying to tell when you are no able to hear a difference between on and off anymore. An ...
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1answer
40 views

On parabolic concave mirror in car flashlights

Sorry for the seemingly silly question but what's the advantage of having a concave mirror in car flashlight? I understand how the physics works but I just don't get what the advantage of having this ...
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0answers
17 views

Would an HI or HII region have a color?

That is, if we were approaching an HI or HII region in a spaceship, would the cloud have a color visible to the naked eye? Of the HI region, Wikipedia says: These regions do not emit detectable ...
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0answers
56 views

Why is 2000 grit good enough for a mirror finish?

The mean particles size on a 2000 grit sandpaper is ~ 1 um, which is not that smooth compared with the wavelength of visible light. But usually when I want a mirror finish, 2000 grit will provide a ...
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2answers
39 views

Derivation of Specific Rotation formula?

This is sort of a weird question, so bear with me: I was reading about how chiral molecules rotate plane polarized light and decided to think of a "logical" formula for expressing the amount that ...
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1answer
34 views

WHY are reflections stronger at an angle acording to the Fresnel equation?

When looking straight at a glass surface you can mostly see through it, but if you look at it at an angle it becomes more and more like a mirror surface. This is described by the Fresnel equation, or ...
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0answers
17 views

Broad Spectrum Contact Lenses - How Soon?

Given the amazing advances in metamaterials, how soon will we have the means to view a broad spectrum of electromagnetic radiation (IR through UV) by having it faithfully compressed into the range of ...
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1answer
42 views

Why does our eyes see red when exposed to too much light? [closed]

When I looked into my projector when it was on the blue screen it left a red spot in my vision. I should not have tried it but all the colors left a red spot. Why not a blue or yellow spot was left?
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5answers
115 views

How comes unpolarized light do not undergo destructive interference?

As far as I know, unpolarized light is defined as light which as no clear axis of polarization, but electric field vectors in all directions. However, I also know that electric fields can be ...
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3answers
117 views

What is the amplitude of a light wave?

Referring to this question How can I measure the amplitude of a light wave? I'm curious about what is a amplitude of a light wave. Especially for light from a thermic source.
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1answer
73 views

How can I measure the amplitude of a light wave?

Suppose I have a light wave and I want to measure its amplitude, or check to see if it has an amplitude of a certain value: how would one go about doing this?
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2answers
96 views

Can't reach speed of light, but relative to who?

Imagine a stationary person (with respect to a spaceship) floating in space and looks at a clock on the spaceship going 0.5c and sees it's clock ticking slower than his own, and concludes that it is ...
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2answers
97 views

Are light waves sinusoidal functions?

I was researching sinusoidal functions when I realized that the wave produced by a wave function looks exactly the same as a light wave. Is a light wave a sinusoidal wave, and can a light wave be ...
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0answers
16 views

Generic Rayleigh effect experiment - nothing happens for water

On youtube, a bunch of Rayleigh scattering experiments (e.g this one are set up with some compound being added to water in order to invoke the effect. Why is there no Rayleigh effect for "pure" water?...
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0answers
23 views

Laser light in a digital display

At my job, I am working with an augmented reality headset and various pairs of laser goggles. The display on the AR headset sits outside of the laser goggles. I've noticed that you can (more or less, ...
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0answers
23 views

Reversibility of Path of Light and refraction at i(c)

After reflection in the below diagram, what would happen: Will it pass all the way at the surface of separation? Will it be refracted back at the critical angle, if so at which point. It seems ...
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0answers
16 views

Photoelectric effect and evanescent fields

We all know that if light impinges upon a metal and if it's the energy of the photon (hv) is greater than the work function of the metal then an electron will become unbound from the metal and be ...
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1answer
26 views

Active light polarization filter

I want to realise a (fast) active light polarization filter. I just need two states: 0° and 90° rotation of the filtering plane. Is it possible to use a "normal" LC film like in displays and just put ...
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1answer
145 views

What´s the origin of the four rays that come out of the reflection of candlelight in our TV?

The reflection of a candlelight in our TV shows four emerging rays. The rays vary spatial and periodical and have a repeating pattern of the colours of the rainbow. The further the flame is from the ...
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4answers
2k views

Difference between sunrise and sunset?

Other than knowing which direction is east and which direction is west, or observing for a sufficient timespan (to determine the direction of motion), is there any way of telling whether what one is ...