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 are most accurate reflective surfaces not white?

Since white is our perception of reflection of light, why are mirrors and other metallic objects that are more grey or silvery capable more reflective than a white object? This is somewhat related: ...
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2answers
358 views

Seeing one's back on the event horizon

If we would hypothetically be exactly on the event horizon, we should see our own back, because of the circular motion of photons on the event horizon, right? But what would be the image size, or $-$ ...
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308 views

Is it possible to transfer light from edge to edge of transparent material?

I don't know much about physics but i believe that this is the place to ask my question. I'm using 3 monitor setup like this: the plastic bezels [ ] are extremely annoying. in order to make them ...
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2answers
1k views

Why doesn't my pinhole camera work?

We all know that light travels in straight a line, which can be proved by pinhole imaging as in the picture shown : But when I'm doing this little experiment with an apple, no matter how I change ...
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2answers
252 views

Sensitivity of eye

In which color human eye is most sensitive?
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2answers
246 views

Why do clouds appear black?

I have noticed clouds appearing black during rain. But I don't know what makes clouds to acquire that colour. This phenomenon doesn't appear every rainfall. There has to be distinction to white ...
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2answers
641 views

How much light is there in space and how heavy is it?

Our night sky is filled with stars. On a dark night a significant fraction of the sky is light. This light, we are told, has been in transit for many millions of years. There must therefore be quite a ...
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4answers
483 views

Light and Gravity - bending of light around a massive body [duplicate]

Well, as I have read, a massive body can cause light to bend around itself due to its gravitational attraction. What I don't understand is how, as the Newtonian formula for the force of gravitational ...
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2answers
672 views

Can a dot of light travel faster than the speed of light? [duplicate]

Say I have a laser. If I spin the laser so that the beam sweeps in an arc along a very distant object, could that dot travel faster than the speed of light? In Diagram form:
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10answers
2k views

Why do we think of light as a wave?

I've read that light travels in a straight line and has a wavelength of 400nm to 700nm. But I don't understand why does it have a wavelength and what creates its wavelength? I agree with the concept ...
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1answer
306 views

Very large absorption lines in stellar spectrum

I was puzzled by the wide absorption lines in a stellar spectrum I found. The following is what I expect absorption lines to look like - thin, crisp lines: However, I found this stellar spectrum, ...
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3answers
698 views

Why do electrons around nucleus radiate light according to classical physics

As I navigate through physics stackexchange, I noticed Electron model under Maxwell's theory. Electrons radiate light when revolving around nucleus? Why is it so obvious? Note that I do not know ...
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2answers
565 views

Calculating the illumination of the moon

I am trying to find a formula that will enable me to calculate the illumination of the moon down to one thousandth of a percent, given that the Gregorian year, month, day, and hour is known. Can ...
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1answer
37 views

Do all narrowband filters tint the field of view?

I observed color in a nebula for the first time this past weekend when looking at the Ring Nebula through my Orion XT8. I noticed a bit of red on the outer edges. I placed my Orion Ultrablock ...
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2answers
89 views

A light so strong it has a shadow

I have recently taken an interest in shadows. I know that in order for a shadow to exist that you must have a solid in the way of the light. My hypothesis is that there can be a light so strong, like ...
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1answer
468 views

What is the meaning of this “let there be light” joke?

A middle school teacher across the restaurant is wearing this shirt, and I certainly don't get it.
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2answers
100 views

Is ocean color affected by Rayleigh Scattering?

We know that sky color is due primarily to Rayleigh scattering. Is Rayleigh scattering the dominant effect for ocean color too?
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2answers
2k views

Why does the Sun feel hotter through a window?

I have this big window in my room that the Sun shines through every morning. When I wake up I usually notice that the Sunlight coming through my window feels hot. Much hotter than it normally does ...
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2answers
302 views

Ways of achieving parallel rays of light?

I am thinking of ways of achieving parallel rays of light. Let's say I have an object that emits light, for instance the display of my mobile phone. The display emits rays of light in every ...
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2answers
432 views

Does diffraction occur before interference?

In the double slit experiment, light passes through two slits and the waves interfere and form an interference pattern. A single slit is required for diffraction. So, I was thinking about whether ...
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2answers
84 views

Why slightly closing your eyes let you see the rainbow colors?

So I was sitting and looked at a street lamp outside my house. It is an ordinary lamp that looks something like that: This lamp emits white light and it is about 20 meters from my house. It was ...
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2answers
143 views

Is a Perfect/Lossless Mirror possible?

In traditional mirrors, some of the input light is absorbed by atoms in the mirrors surface and are 'lost' as heat, degrading the quality of the reflected image. Could this loss be compensated by an ...
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4answers
287 views

Why do the passing objects' shadows run in the direction of the moving train?

While travelling in the train on the sunset, I have noticed the strange phenomenon. The shadows of the lonely trees and lampposts, that stay along the railroad, are moving on the wall in the same ...
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1answer
348 views

Why same formula describing Doppler effect in the case of light in different situations?

I made comparison between Doppler effect in light and sound and one interesting thing that I saw was that in the case of sound there are different formulas to find the apparent frequency in different ...
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1answer
315 views

Photons arriving from the Sun

Given that the Sun is a bit less than 10 light minutes away from Earth, is it correct to assume in principle (I understand actual processes in the core of the Sun make the situation at a photon's ...
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4answers
222 views

Why does it require such little energy to create the fastest thing in the universe?

I have noticed when I turn on the light switch in my house light comes from the bulb. How is this light created?(process occurring in the bulb) and why is this small amount of electricity enough to ...
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2answers
176 views

What are the lines visible between two cards held edge-to-edge?

Hold two cards (say credit cards) edge to edge, anything from a very slight touch to about 1/3 mm separation, in front of any ordinary light source. When I do this I see several fine dark parallel ...
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1answer
777 views

Visible light spectrum to color space

I need to be able to convert an arbitrary emission spectrum in the visible spectrum range (i.e. for every wavelength between 380 and 780, I have a number between 0 and 1 that represents the ...
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1answer
91 views

If I'm running away from chasing gamma photons, I can see them, right?

Suppose Bruce Banner goes back in time, convinced that the Hulk is a stupid menace. Let's say he also borrows Quicksilver's speed abilities (maybe the Flash is more appropriate, but based on the ...
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3answers
322 views

Does optical fiber preserve the angles of incoming light?

I am reading up on optical fibers and there's one thing I haven't understood yet: Does an optical fiber preserve the angles of incoming light? For example, if we light two LEDs in front of an ...
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2answers
152 views

Is light's path a wave?

In a lot of textbooks I see a schematic of light drawn as a squiggly line. I have even heard that some things are too small to be seen because they are smaller than the wavelength of light (and ...
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2answers
254 views

Attenuation mass-thickness for sunset light

We are able to look directly at the sun near sunset and sunrise, which clearly demonstrates the fact that our atmosphere attenuates visible light. Let's imagine it follows the typical attenuation ...
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1answer
452 views

Does light induce an electric current in a conductor?

I know that electromagnetic waves induce electric currents in conductors and that's the basis for radio, wi-fi etc. I also know that light is also an electromagnetic wave. So, can light induce a ...
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1answer
1k views

Transparency of solids using bandgaps and relation to conduction and valence bands

I think I understand how a solid can appear transparent as long as the energy of the photons travelling through it are not absorbed in the material's bandgap. But how does this band gap relate to ...
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3answers
6k views

Why can't light pass through walls but sound can?

When I sit in a room I can hear voices coming from the adjacent room but the light in adjacent room does not enter my room i.e. sound waves travels through the wall but light waves can't. Why?
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1answer
48 views

Why is it hard to make black clothes?

I've noticed that we have so-called 'black' clothes everywhere, I haven't seen so far any piece of clothes that would be really black, it's always some kind of lighter black. For instance, if you ...
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2answers
193 views

If atoms have specific energy levels, why do opaque solids absorb all visible light, not just some? [duplicate]

Here's my question: if atoms have well defined energy levels and those differences correspond to the frequencies of light that can be absorbed, how is it that opaque objects absorb all or most visible ...
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2answers
288 views

Difference between Scattering and Fluorescence

It is often said that substances, objects have color because they selectively absorb all color of sunlight except one. The wavelength that is not absorbed reaches our eyes and we perceive it as ...
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3answers
544 views

Real image with converging lens?

I read in a AQA GCSE book that: A real image is formed by the converging lens if the object is further away from the principal focus/focal point. I did this experiment in class: Here is my ...
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2answers
441 views

Does thin film interference (anti-reflective coating) let more light through?

The theory of an anti-reflective coating is that the reflected light off the coating and the reflected light off the substrate is 180 degrees out of phase, causing destructive interference and ...
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1answer
306 views

Young's double slit experiment viva question

My professor asked me (in my viva exam), "If, in the Fraunhofer single slit diffraction experiment, if we have 2 slits instead of one (at very short distances), What would happen?" I answered with ...
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2answers
1k views

Can 2 beams of ultraviolet light intersect and be visible where they intersect?

Is it possible that if you have 2 ultraviolet lasers, that are invisible to the human eye, and if you aim their beams to intersect at some point, that the place of intersection will show a lower ...
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2answers
71 views

What is the physical structure of light?

Conceptually, I understand what light is, but I don't know what a photon would "look like" if it could be frozen in space/time. For instance, the notion of amplitude seems to be absent when discussing ...
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2answers
147 views

Squinting at light sources

I am sure it's just your eyelashes creating a filtering effects, but if you look a a bright(ish) light source such as a lightbulb while squinting, if looks like you are seeing straight light rays ...
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4answers
215 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 ...
4
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1answer
79 views

Sunrise/Sunset on a planet with an A-Class or B-Class Star

I'm a sci-fi writer, and I have a question regarding a hypothetical planet that orbits an A-class or B-class Star. Assuming Rayleigh Scattering occurs roughly the same way on this planet as it does ...
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3answers
114 views

Possibility for contact lenses that enhance the vibrancy of color

Would it be possible to develop oculars that would enhance the vibrancy of color? I know there are many digital filters to improve vibrancy, but are there physical devices able to produce the same ...
4
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1answer
105 views

What is the intensity of this light?

I am struggling with a derivation that calculates the cross sections for Mie scattering and since the incident light is considered to be a x-polarized plane wave I thought that we would have $$I_i = ...
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1answer
926 views

Gravitational Redshift around a Schwarzschild Black Hole

Let's say that I'm hovering in a rocket at constant spatial coordinates outside a Schwarzschild black hole. I drop a bulb into the black hole, and it emits some light at a distance of $r_e$ from the ...
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1answer
362 views

Was the choice of red/green colors for traffic lights a happy coincidence?

All of us have learned since secondary school that the reason we use red in the traffic lights for "Stop" is because it travels the furthest without dispersion. According to wikipedia which cites ...