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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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 spacial and periodical and have a repeating pattern of the colours of the rainbow. What could be the origin of this ...
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4answers
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 ...
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1answer
25 views

Does closing the shades at night make the room brighter?

Does closing the shades at night make the room brighter? Is the light kept in, or is the dark kept out?
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3answers
326 views

Fringe width and spacing and number of slits in diffraction experiments

In a single slit experiment, the fringes are not equally spaced and aren’t of equal widths—the central maximum is the widest, the secondary maxima grow narrower and narrower outward, and the minima ...
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1answer
61 views

Critical Value for Dispersion of light [on hold]

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 ...
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2answers
21 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 ...
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2answers
3k views

Young's Double Slit experiment question

Q-A beam of light consisting of two wavelenghts 600 nm and 450 nm is used to obtain interference in Young's Double Slit experiment (YDSE). Find the least distance from the central maximum where the ...
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2answers
112 views

At which times does light act as a wave and at which times does it act as a particle? [duplicate]

Is light a "particle", that exists as a photon or as a "wave", the usual electromagnetic wave. If it's both when does it exist as a "particle" or a "wave"?
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2answers
93 views

Unusual phenomenon from fluorescent lightbulb

Next to my bed I have a fluorescent desk lamp. One night, after I had turn off all the lights in my room, I grabbed my blanket from the other end of the bed. As I grabbed the blanket, one end of the ...
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1answer
471 views

Why can I turn light red or blue by holding my finger up to it?

This is a difficult phenomenon to explain. Imagine you have an opaque object partially covering a very bright light source, for example, an object held up against the sky. The left hand diagram is ...
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0answers
22 views

Natural light concentration [closed]

Is it possible to use a stack of conical lenses to bring natural light to a specific focus and from there take it through optical fibers for illumination.
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1answer
111 views

How long will it take to collect enough energy to eject an electron [closed]

A light source with intensity $1\ \mathrm{Wm^{-2}}$ shines on a piece of potassium. The binding energy of the electrons in potassium is $1.8\ \mathrm{eV}$. The “Bohr radius” of an atom is ...
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0answers
51 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 ...
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4answers
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 ...
1
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1answer
61 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 ...
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1answer
39 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?
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0answers
28 views

Light of planets and natural sattelites [closed]

I have been getting stuck while solving and imagining the following problem: According to Plank's quantum theory "Energy radiated or absorbed by a body is not continuous but discontinuous in the form ...
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1answer
30 views

light and sound speed [closed]

why is the speed of light faster in water than it is in air? And why is the speed of sound slower in liquid than it is in air? Is its difference is related to wave's appearance? like transverse wave ...
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1answer
38 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 ...
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0answers
22 views

Distance between objective lens and eyepiece in a compound microscope [closed]

why does the total distance between the objective lens and the eyepiece in a compound microscope needs to be greater than the sum of the focal length of objective lens and focal length of ...
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1answer
36 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 ...
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0answers
76 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 ...
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1answer
7k views

Purple doesn't occur in rainbow - or does it?

Usually, when asked whether the purple color exists rainbows, an answer similar to this is given: The purple color is perceived by human eyes via the activation of both red-sensitive and ...
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1answer
80 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?
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4answers
9k views

Can someone explain the color Pink to me?

I just finished watching this interesting video: http://youtu.be/S9dqJRyk0YM It does a very quick explanation of how pink light doesn't exist, and that the concept of pink is our brain's attempt at ...
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3answers
374 views

What is the significance of wavelength when referring to light (in layman's terms)?

Without any equations or complex terminology, I simply want to understand in complete layman's terms what the significance of a single photon's wavelength is. People say that microwave radiation's ...
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0answers
20 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 ...
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2answers
1k views

Why does the Sun turn red near sunset?

At daytime the Sun's light is yellowish if not near white. Why when the Sun starts to go down that it's light turn more red. I don't think the earth's rotation is so rapid to cause a red shift. Why ...
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1answer
354 views

Solar energy and optical fiber

I'm not really good at science or physics, just wanted to ask about the idea (doesn't have an opportunity to test this). Will this scheme work and what can be its efficiency?(The goal is to make ...
12
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3answers
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 ...
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1answer
39 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 ...
40
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2answers
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 ...
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1answer
27 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.
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1answer
56 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 ...
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1answer
59 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 ...
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0answers
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, ...
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2answers
100 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 ...
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1answer
31 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?
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2answers
549 views

How to use a magnifying glas or any lens to enhance small light power?

I am currently trying to amplify a tiny amount of light so that a photodiode will recognize it. In order to amplify the light I thought about using a magnifying glass since I got to know that such ...
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2answers
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.
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0answers
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 ...
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1answer
33 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 ...
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1answer
61 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 ...
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1answer
59 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 ...
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1answer
60 views

Why does everything written on a page appear in concentric circles when we rotate that page? [closed]

When i put a pencil in the middle of a paper and rotate it very fast, whatsoever is written on it, will appear in concentric circles. What is the reason behind this phenomenon and what is it called?
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0answers
25 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 ...
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1answer
241 views

Dispersion in a rectangular prism

Why are the colours visible only at the fringes of the light refracted through a rectangular prism?
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2answers
525 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 ...
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1answer
24 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 ...
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0answers
41 views

Light, the carrier of information. Is this hypothesis a known phenomenon?

I am seeking clarification on a naive insight that I experienced recently. It seems plausible and may be known to most academics and practitioners in the field but I would appreciate your knowledge ...