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.

learn more… | top users | synonyms (2)

1
vote
3answers
27 views

Diffuse laser light in a surface

Im building a laser target. It consists of a box, with a black plexiglass circle in the center of one of its sides, and a larger white circle around it. The black for the inside shots, and the white ...
1
vote
2answers
4k 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 ...
2
votes
1answer
89 views

Why do we use the index of refraction for yellow light?

When we do problems with optics and refraction, we’re usually given a set of indices of refraction to work with; for example, the index of refraction in air is about 1.00, the index of refraction in ...
0
votes
1answer
45 views

Do parallel rays reflecting at a mirror not intersect at one point? [on hold]

Let's take a concave mirror with $CP$ as its principal axis. Let's assume that a parallel ray $p$ to $CP$ reflects at $A$ to pass through the focal point $F$. Then, $\angle CAF=\angle ACF$, which ...
1
vote
2answers
143 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 ...
0
votes
1answer
35 views

Brightness of light sources

I would like to know what determines the brightness of light.I'm confused,After hours of reading i got these definitions mixed up i need to link them together : Light intensity Brightness of light ...
0
votes
2answers
218 views

Light-matter interaction and an object's appearance

I am taking a course in Computer Graphics, and the teacher said we could put materials in there main categories: mirror like glossy or specular diffuse He suggested that the law of reflection is ...
1
vote
1answer
49 views

Polarization vector identity in Minkowski space?

Playing around with numerical light-like momenta $p^\mu_1,p^\mu_2$ (light-like meaning ${p_1}^\mu {p_1}_\mu={p_2}^\mu {p_2}_\mu=0$) and corresponding polarization vectors ...
0
votes
0answers
27 views

How to actually determine the Index of Refraction of an object in different colors of light?

I would like some guidance as to how the IOR of an object is determined in different colored lights. Taking for example diamond, I know that the base IOR is 2.417, and the respective wavelengths of ...
4
votes
3answers
3k 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 ...
4
votes
5answers
203 views

What about a surface determines its color?

Light falls on a surface. Some wavelengths get absorbed. The other are reflected. The reflected ones are the colors that we perceive to be of the surface. What is the property that determines, what ...
0
votes
0answers
19 views

Variations in electric field of a light speed charged particle

From the question " Is there a travelling speed of for electric field? If yes, what is it?" I get to know electric field propagates at speed of light. What if a charged particle which creates this ...
2
votes
2answers
418 views

Finding the illuminance from a triangular light source

Since most light sources in games are point-like, it's pretty difficult to approximate area light sources with point sources. As triangles are a universal form to represent 3D models (thus area light ...
1
vote
1answer
34 views

Is crystal diffraction actually diffraction?

It seems like a very common model that is taught in schools for crystal diffraction is that there is an incident plane wave of light on a crystal lattice, and each atom in the lattice scatters the ...
4
votes
4answers
852 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 ...
4
votes
2answers
185 views

Light wave crossing media and the relationship between speed, wavelength, and frequency

There are many threads on this topic (like this one) but one aspect about the equation $ v = \lambda\nu $ still confuses me. I have read that frequency does not change when light crosses into ...
3
votes
5answers
4k views

Eye sensitivity & Danger signal [duplicate]

Why are danger signal in red, when the eye is most sensitive to yellow-green? You can check luminosity function for more details...
6
votes
2answers
2k 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 ...
-1
votes
0answers
18 views

Propagation of force thought experiment [duplicate]

Imagine you have a million rigid spheres lined up edge to edge in a way that they can only move in one direction. now imagine that there is a wall at one end of this alignment. If you were to push at ...
0
votes
1answer
34 views

Is there a formula to calculate the deviated angle of a ray passing through a prism?

I'm assuming the angle of incidence to be the number of degrees from a perpendicular line on the side of a prism the ray starts passing through... I'm trying to figure out the angle the ray would be ...
0
votes
1answer
105 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
0answers
48 views

Spectroscopy from a classical light wave or photon only?

In chemistry we mostly regard light/electromagnetic radiation as a beam of particles or photons. This is a very useful model to explain molecular excitations and ionisations from quantum interactions. ...
6
votes
1answer
2k views

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

Someone across the restaurant is wearing this shirt, and I certainly don't get it. Update Related: What does this quote about the four dimensional divergence of an antisymmetric tensor mean?
6
votes
5answers
6k views

Is it (theoretically) physically possible to project an image into thin air?

Is there some law of physics that strictly prohibits the projection of 2D or 3D images into thin air (such as holograms in movies) or is a solution to achieve this still up for grabs by an eventual ...
3
votes
3answers
136 views

How is it possible for the wavelength of light to change in a medium?

So my physics class has just finished a long unit on optics while at the same time I've been trying to teach myself relativity. I admit my understanding is probably rudimentary, but I figured all the ...
1
vote
1answer
117 views

Dispersion in a rectangular prism

Why are the colours visible only at the fringes of the light refracted through a rectangular prism?
1
vote
1answer
36 views

Can you use infra-red goggles (or similar principle) to see through mist and fog?

As per title really... fog is obviously quite opaque to visible light yet transparent to radio waves. What is the range of frequencies at which fog is opaque, and is either end of this range at a ...
3
votes
2answers
156 views

Explain the notion of light/electromagnetic waves/photons to a non-physicist

A non-physicist asked me about special relativity. My explanations naturally were based on gedankenexperiments involving light. This forced the question: "What is light? It is particles, isn't? Or is ...
0
votes
0answers
22 views

Does light follow magnetic flux lines? [duplicate]

Will light naturally tend to align itself to magnetic flux lines?
0
votes
2answers
80 views

Why do sea waves seem to be standing still when you look from the window of an airplane?

Looking from the window of a passenger plane even at moderate altitude such that one can still recognize individual waves and even something like white foam, and small boats close to the cost line, it ...
23
votes
3answers
6k views

Does a photon exert a gravitational pull?

I know a photon has zero rest mass, but it does have plenty of energy. Since energy and mass are equivalent does this mean that a photon (or more practically, a light beam) exerts a gravitational pull ...
35
votes
4answers
4k views

Do rainbows have ultraviolet bands and infrared bands?

We have seen that rainbows looks so colorful as we are only able to see only the visible light. But Do they also have ultraviolet bands and infra-red bands, that we are unable to see? I know someone ...
0
votes
1answer
67 views

Can electrons reflect light?

Lately, I have been watching sparks while connecting my electronic devices and I can notice that electricity is kind of blue, and theoretically it's blue because it reflects blue wavelengths?? And ...
0
votes
2answers
79 views

How can light enter a black hole if it cannot get out?

I have known for a very long time that light cannot exit a black hole. I can even understand some of the simpler reasonning about it, such as escape velocity, or space geometry inside the black hole. ...
0
votes
0answers
12 views

Electrons in a gas discharge tube

I'm having some difficulty understanding regarding electrons in gas discharge tubes. My understanding is the following: In a gas discharge tube the gas must be at low pressure in order to be ...
1
vote
4answers
114 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 ...
2
votes
1answer
36 views

White light to blue light

When white light falls on a blue colored translucent material and passes through it the light changes its color into blue.Similar phenomenon is observed when yellow light passes through red glass in a ...
2
votes
3answers
56 views

Is sunlight truly white?

I recently purchased a book on nuclear astrophysics, with no goal of mastering the topic but merely to read in between exams and hopefully learn something, it is revealed that the sun is composed ...
5
votes
4answers
4k views

How do electromagnetic waves travel in a vacuum?

This is perhaps a total newbie question, and I will try to formulate it the best I can, so here it goes. How does an electromagnetic wave travel through for example, the vacumm of space? I usually ...
7
votes
5answers
2k views

High speed and low speed photons

Looking at the discovery of the neutron, and I came across this page: http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron3_1.htm The animation on the left, talks about low energy photons and ...
0
votes
0answers
16 views

How does a hologram record the incident laser?

How does the hologram (the photographic plate) record the incident laser beams when they hit onto it, what happens inside the hologram so that it records these laser beams?
-1
votes
2answers
61 views

is there a way to capture scenes from past? [closed]

Is there a way to capture scenes from past for ex/ capturing someones sound which lived before long time ago.. if yes, how? and if no, why? Regards
16
votes
6answers
4k views

Can UV light make us invisible?

For an object to create different EM waves, it needs to increase the temperature, so what if we or some material could be so hot, that it would emit ultraviolet light, and thanks to that be invisible ...
0
votes
1answer
22 views

Reflection of light at a microscopic level [duplicate]

I always read that light is reflected by a mirror! My question is how does reflection takes place at microscopic level? Mirror is just atoms and electrons are revolving around the nucleus ! So where ...
0
votes
0answers
13 views

Single slit diffraction and fringe width

I know that intensity of the bright fringes will decrease on moving away from centre and width of the central fringe is 2 times that of the second fringe. Does the width of other bright fringes ...
201
votes
19answers
69k views

A mirror flips left and right, but not up and down

Why is it that when you look in the mirror left and right directions appear flipped, but not the up and down?
0
votes
1answer
31 views

Circularly polarized light and polarizing filter

Does circularly polarized light pass through a linear polarizing filter, regardless of the orientation of such filter?
0
votes
1answer
37 views

Can infrared lasers still do damage to things if they are powerful enough?

So I get that infrared light is not visible to the human eye without some sort of device to assist in helping you see it, but I was just wondering how that plays into things like lasers. I know you ...
1
vote
2answers
604 views

Polarized sunglasses: should the axes in both lenses be parallel?

See the pictures below. A pair of sunglasses I recently purchased has the polarization axis in one lens offset about 20 degrees (by eyeball estimation) from the other. I don't have much experience ...
1
vote
0answers
22 views

YDSE and diffraction

In a single slit diffraction experiment we know that light bends around the edges. So can we treat Young's double slit experiment (YDSE) as a two slit diffraction since we're using two slits in that ...