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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Basic question about light

My understanding is: when light hits an object, it can do one of three things: transmit through the object, be absorbed into the object, or reflect from the object. However, I have also learned that ...
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2answers
251 views

Is light getting another color when travelling through a prism?

When white light travels through a prism the speed of this light is slowed down. Now there is a relation between speed of light, frequency and wavelength. So when a red light of 700nm enters a prism ...
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0answers
18 views

Is there a limit to the frequency of light? [duplicate]

I am assuming that light frequency would eventually be limited by Planck distance and/or Heisenberg limitations. Could this frequency ever be approached in practical terms?
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2answers
252 views

Why is infrared radiation associated with heat?

I am little confused with infrared radiation. I understand that when an object is hotter, it radiates electromagnetic waves of a bigger frequency and this waves are also more energetic, that is why ...
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1answer
42 views

Is it scientifically possible to stop a screens polarization by adding a layer? [closed]

Back story: At work we deal with confidential data, however our desk layout does not allow for screen privacy. We do not a privacy screens and are not allowed to take apart our screens. In searching ...
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1answer
41 views

why my eyesight glasses the color of the things I see?

I have started to need eyesight glasses (I am short-sighted) a while ago and I am puzzled by the fact that when I wear my glasses the color of the things around me are less bright than when I don't ...
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3answers
133 views

Do gravitational waves affect light?

Gravity "bends" light, predicted with theory of relativity and subsequently observed: how does gravity and gravitational waves achieve this effect, and shouldn't this effect be present wherever ...
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0answers
54 views

Cherenkov Luminescence Imaging, Cherenkov radiation,

Is it possible to see glowing from Thin Layer chromatography (TLC silica gel on Aluminium) when we image it by IVIS spectrum (no radioactive source)?
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1answer
32 views

Sphere, silver reflector, refraction questions

A sphere with its back silvered can act as a retroreflector. When a fine beam of light is directed to the sphere as shown, it is refracted at the front surface, and focused on the rear interior ...
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1answer
31 views

Tricky Optics Questions, shifting lenses [closed]

A candle is placed at a fixed distance in front of a wall. A lens is inserted and moved slowly between them. At two particular positions, sharp images are formed on the wall. The heights of the images ...
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1answer
81 views

Given is an object which is cyan when illuminated with white light. What is the perceived colour of the object when illuminated with yellow light?

I know the perceived colour of an object depends on which wavelengths of the incoming light are reflected and not absorbed, which lead me to believe that it is impossible to be red or yellow... I ...
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0answers
32 views

Doppler shift of light from stars and galaxies [duplicate]

I was reading about how we can ascertain whether a cosmic object is receding from or approaching us by studying the doppler shift of its spectrum- I mean the redshift and blue-shift. But we have no ...
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0answers
11 views

Color Temperature Variation of Sunlight

I want to know what is the Variation of the color temperature in Kelvin of Sunlight as viewed from the earth from Sunrise to Brightday to Noon to Sunset. Will there be any change in the color ...
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1answer
43 views

Can two different RGB color triplets give the same color?

It is easy to understand that RGB color models cannot represent all colors. First the coding on a finite number of bits (16, 24...) cannot reproduce the infinite number of tones. Second, the RGB ...
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0answers
16 views

can you concentrate diffuse light?

how do you turn diffuse light into direct light?
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1answer
60 views

Why is glass green?

When I look at a glass block at an angle the edges appear green, but when I look at the edge sideways, so that is directly in front of my eyes it appears transparent. Why?
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1answer
25 views

Diffraction grating (finding number of emission lines)

I came across a question on isaacphysics.org where youre given information about a diffraction grating, the spacing of the gaps and the colour and location (in degrees) of 8 different maxima, of four ...
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1answer
81 views

Why are UV protective eyeware Orange?

Many industrial processes use uv as a curing agent. When one uses such a process, one must protect one's eyes from the radiation. Most uv protective gear I have seen is tinted orange? Does this ...
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0answers
15 views

Frequency combs measurment

How is a frequency comb actually used to measure something? For example: I don't know the length of my pen, so I take a ruler and measure it -- it reads 10 cm, so now I know my pen is 10 cm. From my ...
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0answers
28 views

Is it possible to see an infinite distance in a vacuum, or is this prevented by dispersion? [duplicate]

I just came across the old cliche that describes a star as a "little candle that shines its light so far," and am curious whether, barring obstruction and interference, one might be able to detect a ...
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1answer
36 views

Newtons corpuscular theory

I am learning about the history and evolution of certain physics theories, one being Newtons corpuscular theory. I am reading that Newton predicted the corpuscles, which make up light would travel ...
3
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1answer
76 views

Why purple seems so to similar to red? [duplicate]

Purple lights has the highest frequency among all visible lights, while the red lights is the least frequent one. However, purple seems to be a mix of red and blue to human eyes, why?
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4answers
140 views

Capture the entire light field of a 3D scene and construct a virtual scene

I've been fascinated with light field cameras for quite a while. They are devices that can capture information about the light field emanating from a scene; that is, the intensity of light in a ...
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1answer
39 views

Speed of light in vacuum in special relativity

In special relativity, the speed of visible light is defined as a constant. But visible light is only a small part of the electromagnetism field. So why?
3
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1answer
47 views

Is the photoelectric effect 'Ionising Radiation'?

According to the definition on Wikipedia, ionising radiation is radiation which has sufficient energy to remove an electron from an atom. So a high energy gamma ray is definitely ionising, but visible ...
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1answer
52 views

Stacked motors thought experiment

first of all, I'm not a mathematician, just curious about something that came up to my mind and maybe you can help me out. Scenario: I have a motor that spins let's say at 20K revolutions per ...
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1answer
901 views

Why is everything not transparent? [duplicate]

There is a related question on this site here: Why glass is transparent? Which explains that glass is transparent because the atoms in glass have very large energy differences between energy levels ...
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2answers
40 views

Double slit with opposite circular polarizers

Let's say I'll send linearly polarized light onto double slit but in front of one slit I'll have quarter wave plate and before the other I'll have 3/4th wave plate (half+quarter? minus quarter?) ...
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3answers
54 views

Can electrons emit light when they are independent? [duplicate]

If an electron is independent, it is an individual electron, i.e. not in the orbit of the atom. Is it able to emit light or does the orbit have to do with the production of light?
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32 views

Splitting an image in a lens into two sources?

Is it possible to project an image of light that passes into a lens onto two surfaces without affecting the image?
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1answer
61 views

What Color Are Black Holes Really? (Yes, a serious question)

So I got into a mini-debate in science class today because I proposed that black holes aren't really black, they only look black because light can't reflect off them. But if you were to take the ...
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4answers
136 views

Why do the edges of glass blocks create a shadow?

I have always observed that the shadow of glass blocks becomes darker as the glass is moved away from the surface where the shadow falls. And I know this is because refracted light rays from the glass ...
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0answers
51 views

Why does Light change color through Glass slab?

I shone a green laser light(~532 nm) through a glass slab and what I saw inside was that the light beam was now red. Imagine a regular refraction diagram but color the beam outside green and that on ...
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2answers
48 views

Physics : Light [closed]

Let us assume that 4 person s are sitting on 4 corner of square ABCD. All have their eye on same level from ground.person looks person diagonally. Now when light goes from A toC and B to D then rays ...
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2answers
82 views

Does an object travelling at the speed of light cast a shadow? [closed]

Asked by my 8yo today and left me scratching my head.
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0answers
17 views

Transmittance of yellow light through blue substance

I am performing an experiment in which I flash an LED-light through a substance with different opacities and do voltage measurements over a photoresistor on the other side. When I decrease the ...
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0answers
37 views

Why do different color materal differ temperature in the same sunlight?

I have a blue, red, and green cup and put a thermometer in each. Of the 3 the blue cup had the coldest temperature inside, then green, then red. I understand there may be differences in the ...
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1answer
22 views

Diffraction pattern from laser shone on coffe-filter plastered on glass pane

I make an ordinary coffe filter wet and plaster it on a glass pane. I then shine a laser onto the filter (on the side of the pane with the coffe filter). When I do this, I see what I assume is an ...
4
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1answer
53 views

How much of Ultraviolet is cut out when Sun moves to the Horizon?

EDIT: Original question was whether or not we need to wear sunglasses when Sun is at the horizon. But it was confusing to many users whether it is on-topic or not. So the details are adjusted. From ...
3
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1answer
41 views

Momentum transfer of Light to Object

Can light made of photons in theory topple lets say a car? I know basic photon energy is hv where v is frequency. So according to conservation of linear momentum, if high enough and large amount of ...
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0answers
9 views

Mueller matrix and Lorentz group

I have just learned about Stokes vectors and Mueller matrices for description of polarized light. In the text I studied there is clear restriction for the Stokes vector $\vec S$ that ...
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1answer
41 views

Particle nature of light [closed]

How particle nature of light can be observed in material world? To common man light does not hit them or make them fall when light beam is projected on them.
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1answer
81 views

Characteristics of electromagnetic radiation

Is it possible to change the wavelength of an electromagnetic wave without a change of medium?
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4answers
4k views

Why does moonlight have a lower color temperature?

Moonlight has a color temperature of 4100K, while sunlight has a higher color temperature of more than 5000K. But objects illuminated by moonlight don't look yellower to the eye. They look bluer. ...
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0answers
26 views

Light through micro-perforation [closed]

I am trying to have a metal film with micro-perforation lit from one side by LED so that only the perforated pattern appears on the other. Example: Misfit Shine How do I calculate the film ...
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0answers
40 views

Question related to optics [closed]

My teacher asked me a question, the question is this "Sunlight enters into a room thorugh a triangular aperture, when i place a screen nearer to the aperture it casts a triangular image, but when the ...
0
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1answer
17 views

What is the difference between 'Illumination' and 'Illuminance', if any?

What is the difference between 'Illumination' and 'Illuminance', if any? From my knowledge, both of them have the same unit, the lux. So are the two words used to refer to the same parameter or are ...
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1answer
25 views

Why are some Air Gap Sparks Orange?

While testing the ignition system on my car with a variable gap spark tester I noticed that the spark was orange. I suspect that there may be a problem with the ignition coil such that there is ...
2
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0answers
50 views

Lenses that pixeliate incoming light [closed]

Is it possible to make a lens that 'pixelates' the light passing through it? I imagine a pair of glasses, that when put on, turn the world into a grid of discrete pixels, each having, or appearing to ...
1
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1answer
57 views

How are professional laser shows done [closed]

How are professional laser shows done ? I need an explanation of the phenomenon of a laser visible in mid air ,(NOT THE APPARATUS USED which means I don't want the engineering aspect of it,I only want ...