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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How did Cavendish measure the deviation of light from the Sun?

On today's date in 1731 was born Henry Cavendish. He is mainly know for his Chemistry research, however, while I was reading his biography I've noticed that he also calculated the bending of light due ...
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2answers
85 views

Is it possible for two strong lenses to cancel each other effects?

Is it possible for a lens system for 2 strong lenses to cancel each other, so it looks almost the same as a common glass, while at the same time making an object in between them appear big and ...
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1answer
100 views

How can travelling at light speed affect light itself? [duplicate]

~Hypothetical Scenario: Your driving in a car (with the headlights on high beam) and you gradually get faster until you reach the speed of light. Raised Assumptions: You can see in and out of the ...
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0answers
33 views

Why can we treat (most) metals classically at room temperature?

When we consider how light and metals interact with each other at room temperature, the Drude model, which is a classical theory, is usually and successfully used. My lecturer explained something ...
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2answers
97 views

How does thin film interference work?

So thin film interference is when light is half-reflected half-refracted then the reflected and refracted wave interfere with each other to produce another color. What I don't understand is that the ...
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3answers
77 views

How does color (or reflection in general) work?

I'm confused, does the absorption and emission determine the color of something? Or does that only happen when something is emitting energy? When light hits an object, the photons get absorbed, then ...
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2answers
48 views

Diffraction of light

If $l_1$ and $l_2$ are parallel how can they both can hit same spot? Why their difference in path length is $l_2 - l_1 = d \sin \theta$ instead of 0?
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1answer
52 views

clouds reflective property

I am a private pilot and see some beautiful clouds in all forms and patterns up in the sky. I wonder what causes some of the clouds to be so shiny, reflecting such an intense light that it's hard to ...
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1answer
46 views

Interactions of light with the air

This is an interesting thought which I had when driving home today looking in my wing mirrors. If you are driving a car and looking in your, say, right wing mirror, you see an image of the car ...
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3answers
2k views

Why does water reflect light?

Why does water reflect light? What is actually happening when light is reflected by water? We know why metals reflect light; water, however, is not metal, but it still reflects light and we can see ...
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2answers
160 views

Is it possible to mix a luminescent drink? [closed]

Is it possible to create a drink that glows? In other words, is it possible to create a non-poisonous drink that fluoresces? Are there known compounds suitable for that? If not, then what about a ...
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4answers
639 views

Why is light in vacuum so slow? [duplicate]

Accepting the speed of light in vacuum and infinite mass and all that, I wonder why light does not have infinite speed? I know light does not have rest mass, but people use the term infinite mass ...
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2answers
112 views

See the opposite wall on a mirror [closed]

I'm in tenth standard. This is a higher-order-thinking-skills Q I found in a book. One is supposed to use laws of reflection ($\angle i = \angle r$). You can also use mathematical concepts like ...
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1answer
109 views

Number of photons

When a light source blinks, it "creates" a ball of photons, expanding by speed of light. How many photons are there in one "layer" of the ball (no matter how long is the source active)? Is it a ...
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2answers
123 views

Light always particle in vacuum because it has no medium

My physics teacher told me that light in a vacuum is always in the particle form. So what happens if you perform the double slit experiment in vacuum? Will the light spread like a wave or will it have ...
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5answers
4k views

Why can't we see infrared light?

While explaining to my nephew about the physics of light, I told him we cannot see infrared color, and he kicked back with a very simple question: why can't we see it? I could not tell him. Is the ...
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0answers
145 views

What is this bright spot in the sky?

This is my first question here so please be gentle! I took this picutre a few minutes ago (35 minutes ago, currently 1828 here) As you can see there's a VERY bright spot on the right that shows a ...
3
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1answer
131 views

If light is affected by gravity, does that mean gravity affects electrical&magnetic fields too?

Since we observed that masses indeed bend the light, and since we consider light to be composed of electrical and magnetic fields, does that mean a single point charge will result with bent electrical ...
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1answer
51 views

Differences in speed of light calculations in glass

I wanted to determine the speed of light in glass by using both of the following formulas : $$v = \frac{1}{\sqrt{\mu \epsilon}} \simeq \frac{1}{\sqrt{\mu_0 \epsilon_r \epsilon_0}} \;\;\; \text{and} ...
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1answer
322 views

How to measure blue light at home?

I know that we can measure light intensity using a simple 'light meter' and I know that 'blue light' emitted by LCD monitors is in $400-470\,\mathrm{nm}$ spectrum. Since I have sensitive eyes, I want ...
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1answer
55 views

Why we do not consider trajectories for photons/lightlike curves/radiation? I am having a term confusion

Lately I have asked a question about the trajectory of photons and almost everyone told me that I shouldn't talk about trajectories. Also people talked about photons, lightlike curves, light, ...
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4answers
111 views

How does light travel?

How does light travel, does this not contradict the idea that going the speed of light stops time? Because if going the speed of light stops time and light goes the speed of light shouldn't it be ...
0
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1answer
128 views

define narrow band and broadband in Infrared light source

I have an infrared transmitter where the specification sheet says Broadband Emission from 400 to 2200 nm Does this mean it will transmit all mixed wavelength of infrared light between 400 to ...
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2answers
149 views

Speed of light in teflon

I was wondering why some websites are talking about the speed of light in teflon because it seems (tell me if I'm wrong) that it is an opaque material. Or are they talking about the light as an ...
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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
29 views

Coloring the clouds with lasers

What strength of laser would be needed to color or make projections of images upon clouds in the sky? I am assuming that this is possible, if not, please explain why. For the purposes of this ...
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1answer
73 views

How mirages forms and how diamonds sparkle? [duplicate]

How mirages forms? How diamonds sparkle? What is major cause happening for it and can you explain with examples?
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3answers
2k views

Looking at the sun through heavy fog, do invisible wavelengths get through?

This morning it was particularly foggy and my son was excitedly looking at the sun through the fog, since of course he normally can't look directly at it and see the disk. I told him to stop looking ...
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2answers
879 views

Why fast eye movement splits a white LED into the RGB components?

I have a "white" LED as the notification light on my phone. When I look at it straight it looks whitish, but when I move my eyes around (or shake my head) I suddenly see glimpses of red and green (and ...
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0answers
104 views

How to calculate photons/light trajectory under gravity

I'm aware many questions are out there asking similar questions about photons and gravity and I got the basic concept by searching through them. I will just call it light although it may not be the ...
6
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4answers
771 views

Why is the sky blue: For a 3-year old [duplicate]

My nephew asked me yesterday why the sky was blue. I tried to explain it to him as best and as dumbly I could, but I failed. I tried to explain the concept of scattering of light using an analogy of ...
3
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2answers
313 views

Can I use fluorescent light bulbs to calculate Planck's constant?

We did an experiment today to calculate Planck's constant, $h$. We measured the knee voltages $V$ of different LEDs (red, green, orange, blue, violet) and plotted them against the frequencies $f$ of ...
5
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5answers
187 views

What would the RBG color value of an infinitely hot blackbody be?

In other words, what is the limit of the rgb values of color temperature as temperature approaches infinity? Put differently, what is the terminal point of the Planckian locus? Is there an exact ...
2
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1answer
133 views

Why does the laser change colour? [duplicate]

In the first image, the laser colour is green. When it is shined on the plastic cap of the pink highlighter, the colour changes, why has this happened? Tech Details about the Laser Source are; Max ...
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1answer
32 views

Reflection on glass at not the critical angle

I observed many a time that the incident light ray, even not at the critical angle, suffers reflection. Can I know why?
2
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1answer
266 views

Does laser beam expand along distance or not? [duplicate]

Why does laser dot become bigger at bigger distance? e.g: from millimeter to inches so that it distracts pilots in aircrafts. I knew that laser beam should't expand over distance, but remain stable. ...
0
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1answer
94 views

If electromagnetic waves can be generated by oscillation of a coil why can't light? [duplicate]

I was recently reading how electromagnetic waves are generated using oscillation of a current in an antenna. Why is it that this principle cannot be used to generate light?
3
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2answers
173 views

Why is sunlight not violet in color?

I have a UV lamp which appears violet in color, but our own sun also emits UV rays so where does the violet go? Why does sunlight not appear violet?
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2answers
111 views

Smallest object resolvable by optical microscopy

I am wondering what is the smallest object you can resolve with an optical microscope. I am aware of the equation $\delta=\frac{\lambda}{2\textrm{NA}}$ that basically gives you the resolution. ...
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1answer
63 views

Why we use wavelength to divide light into rays, wave and particles?

I want to ask something about light, light can be defined as ray, wave, or particle. The group formed because of the wavelength, if the wavelength is less than the dimension of equipment it is grouped ...
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2answers
84 views

What would/does it look like if your eyes see an object from 2 different times in the same moment?

I don't know pretty much about physics and I'm sorry if there is something I should know that simply makes it clear this couldn't happen. But I asked this myself now already several times and decided ...
0
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1answer
56 views

Is reflection actually due to very low critical angle?

When we take an example of a plane mirror, does the reflection occur because the critical angle for the silvered surface is very small? Are all the good reflectors good at reflecting because their ...
4
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1answer
73 views

How to obtain initial conditions to image Kerr black hole?

I'm reading Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar to make a raytracer code to image Kerr black holes. The paper introduces a Fiducial Observer ...
3
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2answers
142 views

Can light absorb energy?

Everybody knows that all physics systems absorb light quanta, any material thing can absorb light quanta. But the reverse question is , can light absorb energy and therefore changes its frequency? If ...
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3answers
6k views

Why are there no stars visible in this photograph?

Pluto and Charon, photo taken by New Horizons on July 8, 2015 from a distance of 6 gigameters. it's hard for me to believe there were no stars behind the twin dwarf planets in the field of vision. ...
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1answer
98 views

A material with very high refractive index

Suppose we have a material which has a very, very high refractive index, say 30-50. The critical angle for this material would be very small (1.5-2 degrees). Will the said object be even visible at ...
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1answer
156 views

What makes metal change its color during heating?

What happens on atomic and molecular level? Is this true also for non-metals and metalloids?
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2answers
200 views

Light and momentum question? [duplicate]

Each photon of light bulb carries momentum. Why does the light bulb not recoil from conservation of momentum?
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0answers
24 views

Geometric and radiometric distribution of light

I'm studying the behavior of the light in a scene, to know how much light arrives at a specific point of a surface and how much of it leaves from the point. From the documentation I'm reading, it says ...
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0answers
56 views

Does Light have Weight?

If I light a torch and hold it against a wall, will the wall feel any force? If yes, what factors does the magnitude of such a force depend upon? (Area of the wall covered by the beam, intensity of ...