# 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.

41 views

### Duality in Electromagnetic Spectrum

Is visible light the only portion of the electromagnetic spectrum that exhibits particle/wave duality? If so, how/why do other frequencies (i.e. radio) behave as waves?
95 views

For a Physics lab, this question was asked "As you learned, the wavelength and the separation of the sources affect the number of nodal lines produced. Using your results from steps 2 and 3, determine ...
286 views

### Why does light from a laser end up in a concentrated spot?

I've heard from several people that photons will always take the past of least action while travelling, so why does laser light projected on a surface appear concentrated to a single spot when ...
857 views

### What's the intensity of a laser pointer?

The unit of intensity or the irradiance of the light is $\mathrm{W/m^2}$. So what's the intensity of a light pointer? Searching on the web, the laser pointer's power is about $5\mathrm{mW}$, imagine ...
366 views

### Tunable Optical Band Pass Filter

Is there any cheap method by which to create tune-able optical band pass filter? I am working with a chemical process which will fluoresce when excited by a specific wavelength of light. As shown in ...
16k 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 vacuum of space? I usually ...
160 views

### When does a monochromatic beam of light on a reflective surface get completely transmitted?

My book says when when a monochromatic beam of light is normally incident on reflective surface it gets completely transmitted. I am bit confused could you explain me?
146 views

### Detecting a light ray without disturbing it

If I have a light ray trapped between two very reflective surfaces such that the light ray doesn't dissipate, how exactly can I know that there IS a light ray there, without disturbing it? As far as I ...
65 views

### Are there multiple ways to create the same color?

Color is formed by mixing light of different wavelengths, so a color could be represented as a function which gives the amount of light of each wavelength. My question is, if white light is a mix of ...
150 views

### Capturing a light beam

For a given container made of an extremely reflective surface, is it possible to shine a beam of light in, and with no 'fiddling' (i.e. closing the hole, tilting the object) to contain the beam for an ...
2k views

### Why do we assume that rays from infinity are parallel?

If light rays are parallel to each other , if they are from infinity, they are not gonna make an image because they won't intersect with each other. So we are not gonna see the image. Does that means ...
418 views

My room has a single light bulb. It's a bit grim, so I decide to decorate. I have a choice of two lampshades. Both are paper ball designs. One has twice the diameter of the other. The paper is the ...
387 views

### How would a sound mirror work?

Context: We all know that by galvanizing a plate with a silver coating, this plate will have a very high reflection coefficient and act as a mirror for EM radiation (not for all $\lambda$ ranges of ...
138 views

### Why does yellow line on road seem white at night?

I have observed while driving at night the yellow marks on road seem white. What I understand is the color of an object is the visible light wavelengths it does not absorb. In other words the yellow ...
95 views

### An accelerated charge produces an electromagnetic wave. Is light an electromagnetic wave despite not having charged particles? [duplicate]

Light is an electromagnetic radiation contrary to the law of electromagnetism that states that: an accelerated charge produce electromagnetic wave. Please explain.
55 views

### What properties affect the color of item?

I already understand how gap bands work and how atoms can absorb/reflect light. I also already understand that rough objects will reflect light differently in comparison to smooth objects, but I do ...
76 views

### One color frequency items

I asked a slightly different question before, but how common are one color frequency items? Many things can reflect many colors of light, but predominantly show one under white light. If they are ...
3k views

### Why is the light reflected at the same angle from mirror?

From the school physics I know that the material objects bounce from the plane surface at the same angle, losing some kinetic energy. In the same school I was taught that the light (and waves in ...
116 views

### Why are some elemental materials grey?

How does grey occur in elemental materials such as metals? I believe that grey arises from the simultaneous reflection and absorption of all colors of the spectrum (in different atoms of course), as ...
17 views

### Are there any pigments which can be altered via the use of electricty?

I was looking at alternative visual output methods for computer, phone and the like and was wondering, are there pigments, Red, Green and Blue preferably, that can have their intensity/opacity ...
493 views

### Coherence length requirement for interference

One property of light sources that is usually stated, which is of particular importance when trying to create interference fringes, is the coherence length (or coherence time). The equation for the ...
12k views

### What happens if you remove the polarization filter from a computer monitor?

Have a look at this youtube video (and some extra footage here). Here I will post a gif showing in short what it is about: It shows that if you remove the polarizing filter from a pc's monitor and ...
158 views

### Why does the ray bend only in one direction?

By snell's law , the refracted ray bend away or towards the normal according to refractive index of the medium. But it can be seen that the refracted ray bends to the right by an angle when a ray of ...
4k views

### What makes Sun's light travel as parallel beams towards earth?

Sun's light appear to travel as parallel beams towards earth $_1$. Sun produces electromagnetic radiations through pp chain and other reactions in Photosphere $_2$. I don't see whether these ...
47 views

### Can we convert light to another spectrum?

Could we convert light from one spectrum to another just like how it does in a radium, using some device? If we could do that to a specific part of the emitted light, probably we could make 3-D ...
384 views

### Why can't we produce visible light from a radio transmitter? [duplicate]

Producing visible light from a radio wave transmitter: why is it not possible? If it is, what are the limitations?
698 views

### Relation between wavelength and system size

We always say that when a given light wave interacts with atoms bound in a molecule, only waves with wavelength close to the inter-atomic-spacing are able to probe the system. In other context (...
546 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 ...
106 views

### Is there a material that could “convert” near infrared frequency to infrared?

I have a laser with a wavelength of 650 nm (visible red light) and was wondering if there is some sort of material that could be used to absorb and disperse a different frequency of light around (900 ...
142 views

### Does polarization remove any of the fields completely?

A light is made up of electric and magnetic fields oriented perpendicular to each other. Can polarization lead to the removal of any of the fields completely?
109 views

### Light in a box with positron walls instead of electrons

I understand that with a hollow cube with the inner walls covered in mirrors given a light source briefly, the light would eventually be absorbed. This is due to electron excitation I believe. So ...
410 views

### Non-polarised light

We know the beam of light oscillates in electric field and magnetic field, both perpendicular to both the wave of propagation and each other. What does, however, a non-polarised beam of light look ...
590 views

### How can a 360 Degree Rainbow be formed? [duplicate]

Just a while ago while I was reading news paper, I saw an amazing article. Someone had caught a photo of a 360 Degree Rainbow. But how is it possible. I mean after refraction the only rainbows that ...
153 views

### Is light emitted in zitterbewegung? [duplicate]

Recently I heard of Zitterbewegung, a trembling motion of the electrons in atoms that arises from Dirac's equation. I know that, according to Bohr's model, light is emitted when the electron "jumps" ...
594 views

### What does amplitude in wavelength of light physically mean?What oscilates with time in photon?

Like amplitude in wavelength of water waves signify the displacement of water particles about their mean position.
5k views

### How does light speed up after coming out of a glass slab?

As I learned today in school, my teacher told me that when light enters a glass slab it slows down due to the change in density and it speeds up as it goes out of the glass slab. This causes a lateral ...
314 views

### How do I calculate the apparent brightness of a mirror reflecting the sun at a given distance?

I've stumbled around trying to figure this out, but it just isn't my area and I haven't gotten far. This is for writing about an idea of a field of mirrors on the moon, on the terminator when the moon ...
239 views

### Does irregular reflection form images?

In one of my test papers at school, we had a true-false question which said "Irregular reflection can form an image." I marked it true, however I was not given any marks for the question. I asked my ...
68 views

### Radiance increase via two sources [closed]

Can two sources of white light shined at the same general location increase the resulting rasiance?
41 views

### Dynamic equations for propagation of light through dust

For smoothly inhomogeneous media light propagation can be modeled by Maxwell's equations with non-constant $\varepsilon$ and $\mu$. This allows to relatively easily model propagation in the medium ...
66 views

### Physical effects on light from stars

I was thinking about how we see stars at a distance, the light that travels from them is affected by the Earths atmosphere, gravitational lensing and dust etc., but there doesn't appear any equation ...
61 views

### Can we get a true negative of an image reversing the spectrum?

In photography the negative means the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest. But I was wondering: is this the way how negative should ...
83 views

### Bending light (photons) into an orbit

I was wondering and researching about light bending and reflection - I'm wondering if its possible to bend a light beam into a loop (orbit)? I know that light can be bent and reflected (even 100% ...
6k views

### How would night sky look like if the speed of light was infinite?

Would it be brighter? Different color? Gravitational lensing? Would black holes exist?
304 views

### Space orientation of light waves

Recently I've started to be really intrigued with the electromagnetic spectrum and bumped into this problem: According to the wave theory of light (or any electromagnetic wave, really), the magnetic ...
3k views

### How far can light go?

When a ray of light is projected, (say) from the surface of Earth to outside in space. The condition is that, there is no obstruction to it till infinity (it travels only in vaccum). My question is ...
441 views

### Plane polarized light?

I have heard about plane polarized light: light wave which has vibration in one plane. My curiosity forces me to ask a doubt, is there any way to produce polarized light wave which has vibrations in ...
29 views

### What property of medium is directly related to light propagation speed in that medium? [duplicate]

Refractive index is used to calculate phase velocity of light in medium, other than vacuum. Recently I had a discussion with somebody claiming that light is slower due to magnetic field of atoms. I ...