# Tagged Questions

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.

21 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, ...
18 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 ...
15 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 ...
24 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 ...
142 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 ...
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 ...
62 views

### Critical Value for Dispersion of light [closed]

If there is a ray of light moving from $n_1$ to $n_2$ you can get dispersion if $n_1$ is a function of wavelength. What angle of incidence ($\theta_1$) will maximise the dispersion? My solution so ...
24 views

### Beam of light from glass to air

I am reviewing some concepts on light and came across a question that puzzled me. A beam of light is incident from a glass into air. The incident ray is 60 degrees to the normal. The question actually ...
154 views

### How do light waves get their size?

An atom or (small) molecule has the size of about 100pm. Elektromagnetic waves range from about 0.1nm up to 1 km. The most common way waves (like light) are caused by 'jumping' electrons to another ...
56 views

### Seeing light source from its diffracted light

Even if the line of sight is blocked by something(like a wall as in figure) will I able to see the light source if I see the diffracted light of the source? 1.Will the observer no. 2 see the light ...
4k views

### How do those T-shirts that change color in the sun work?

When I was a kid, I asked my dad about them and he said (not in so many words) that it was because sunlight and artificial light have different spectrums and they picked colors that reflect only the ...
40 views

### can the behavior of light be explained on the basis of a single theory?

Can the behavior of light be explained on the basis of a single theory ? example, wave theory of light ,if not then why?
65 views

### The sun glows bright white, but what color of light does it reflect?

Basically if you take a gray iron bar, and heat it red hot, it would still reflect a dullish white light, even though all you could see is the red light it emits as radiation. In fact if you watch ...
39 views

### Calculating wavelengths from angles in a diffraction grating? [closed]

I am having some problems calculating wavelengths from some given information about a grating spectrum. A diffraction grating with a spacing of 3μm is used in a spectrometer to investigate the ...
83 views

### The path that a light beam takes in empty space

First excuse me if this question is very simple for you but for me and for my friend is not. Recently we were discussing what path a light beam will follow in a box moving at a constant velocity in ...
96 views

### Can you see yourself in space? [closed]

Can one see them self in space if no near by star was in view? Is there enough star light to read once your eyes adjust?
30 views

### Sun light collimation

Is it possible to make sun light collimated in such a way, to increase energy density and keep it more less parallel? like on the Earth we have intensity of sun approximately 1300 watt/m2. If we use ...
38 views

### The colour of clouds

Clouds can be a variation of grays, from white to some dark gray, almost black. They are clearly grayscale, so it means they reflect all colours uniformly, but some clouds are whiter than others, so ...
51 views

### Is a narrow beam of light inconsistent with light as waves?

Apparently light can be sent out in very narrow beams. That is easy to understand as particles. However, I don’t know of any way to send waves as a narrow beam. Of course I’m thinking of things ...
4k views

### Why does light act differently in miniatures?

When painting miniatures (like RPG fantasy miniature soldiers)... why is it necessary to paint lights and shadows? Being a 3D object, shouldn't the natural light be enough to create lights and ...
31 views

### How does a flashlight work? How would that be effected in the vacuum of space or on another planet? [closed]

I was wondering if it was possible to explore the dark side of the moon. I've been trying to figure out a light source so things there can be seen.
73 views

### Is it possible to have light without heat? [duplicate]

I am trying to think of a light source that doesn't generate heat; but I am not sure if such a phenomenon exists. I am not referring to passive light (such as reflected light, ie, moonlight) but an ...
61 views

### what do we mean by speed of light dependent on direction?

I have a statement in textbook saying "When the speed of light is independent of direction,the secondary waves are spherical". Can someone tell when it is dependent on direction and how the secondary ...
24 views

### Why is it that light bends towards gravity when it has no mass at all? [duplicate]

Why is it that light bends towards gravity when it has no mass at all? Is it because of how gravity behaves as mentioned in general relativity? As far as I know, light cannot escape from black holes, ...
108 views

### Why doesn't sunlight flicker like candle or flame torch?

Why sunlight appears constant and stable like sun is a bulb? If the surface of the sun and processes going in it are not completely uniform why don't we notice any flickering or non- uniformity in ...
47 views

### Interference of light waves

So my problem now is how do I add the intensities of the resultants of the two constructive interferences. Thanks in advance. Don't hesitate in asking me anything related to the question.
19 views

### addition of two lenses with a finite separation in between

Suppose there are two lenses with focal length $f_1$ and $f_2$ respectively. The effective focal length $f$ when they are combined is $1/f=1/f_1+1/f_2$, but this formula assumes the separation between ...
62 views

### About the earths core being 2 1/2 years younger than the surface

In April's addition of New Scientist there is an article on page 10 by Jacob Aron. This article describes how Earth's core because of time dilations could be 2 1/2 years younger than it's surface. Or ...
35 views

### Why don't conductive objects change color when electric dipoles are induced in them?

I was playing around with a comb, my hair, and pieces of paper when it occurred to me that inducing a dipole on the pieces of paper meant that many valence electrons previously on the side closer to ...
62 views

### How do electromagnetic waves/light travel at the speed of light?

When something reaches the speed of light, then time is said to stop, or at least is perceived to have stopped. The reason is that at that speed, the object become infinitely heavy and requires ...
26 views

### Why is light redshifted?

I heard that very distant stars can be seen as red. Why does light become more 'redder' when travelling long distances? My guess would be it loses some sort of energy, but can't seem to figure it out ...
43 views

### Calculating angle of min deviation of prism [closed]

Two rays incident with angle 40 and 60 on one face of equilateral triangular prism the angle of deviation are equal .find angle of minimum deviation?
26 views

### Reflection and angle of refraction

Does the angle of refraction depend on the properties of the material if the angle of the incidence is the same for two different materials? Say I shed light on a surface with angle $\theta$ and ...
2k views

### How come light waves don't get caught and absorbed by the electrons of oxygen atoms in the in air?

Shouldn't air be opaque since instead of coming into our eye, the lightwaves get caught in the electrons? If oxygen does absorb light waves, how come air is not hot and you can see through it? The way ...
46 views

### special relativity mirror experiment

There's an experiment in special relativity that involves a light source and a mirror, both placed in a moving object. It is used to derive the time dilation equation. I'm having serious doubts about ...
77 views

### Are one photon at-a-time experiments regarded as the Quantum versions of Classical experiments? [closed]

Is it a correct distinction to regard classical experiments conducted one photon at-a-time as the quantum version of the experiments? For instance, if we take Young's original double-slit, and convert ...
30 views

### Structured light, infinite focus

Im interested in projecting a static image across a room that stays focused over a wide range of distances from the projector, without re-adjustment, for a structured light setup. ie, the target may ...
29 views

### Diffraction grating electron velocity problem

Suppose that visible light incident on a diffraction grating with slit distance (space) of $0.01*10^{-3}$ has the first max at the angle of $3.6^{o}$ from the central peak. Suppose electrons can be ...
100 views

### How can unpolarised light be produced from 2 beams with orthogonal polarisation?

Say I have 2 beams of equal intensity with orthogonal polarisation. Is there a way, using linear polarizers, half and quarter waveplates , to combine those two beams in such a way that they produce an ...
86 views

### If photons end up having a tiny mass, say $10^{-54}~\rm kg$, what would be the universal speed of massless particles?

First, I'm no expert so sorry if I get anything confused but I tried to research as much as could before asking this. So while it is pretty much accepted that photons are massless (Despite this ...
25 views

### Refraction of light [duplicate]

In a prism, violet light undergoes more refraction than light of higher wavelength. Is there any explanation as to why light of higher frequencies refract more than light of lower frequencies?
24 views

### Orbital Velocity & LLR

As I understand it, light that is emitted from a source is not imparted with the motion of the source and so always follows a "straight line". If this is correct, I am having a difficult time ...
46 views

### Why does melted agarose in solution appear fully transparent, but become opaque when polymerized?

Agarose gels (hydrogels) are commonly used in molecular biology for electrophoresis of DNA. When a solution of hot agarose is poured, the material is clear: When a gel forms, the material ...
72 views

### Rainbow Black Hole [closed]

In the photon sphere of a black hole the photons are being trapped in orbit, pulled in and trajectories changed. From a safe distance should we see color from the entire spectrum if light in the ...
31 views

### How can we orient light in vacuum?

Let's consider the mirror clock used to show time dilation in special relativity: In the rest frame of the clock, the light pulse from the laser pen propagates in vertical direction down then up: ...
48 views

### Frequency of other light in white light [closed]

I have this question in mind because I read that the frequency of light depends only on the source of light. If we consider a source of white light then it emits light of different colours also. Then ...
55 views

### Do all solid objects emit visible light?

Are there solid objects that do not emit visible light? To my limited and humble knowledge, creating such an object would require us to "only" shift the spectrum of emitted radiation. Is it possible? ...
49 views

### Does visible light heat things up?

During a sunny day the walls of my house warm up (no surprise). My question: how much of this warming up (if any) comes from visible light? I associate infrared with thermal energy. If my house was ...
I don't understand $E=mc^2$ very well, and here is my question: Does this equation mean masses are just condensed energy? And does this mean that the extra energy an object has when traveling at ...