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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3
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6answers
241 views

Bending of light from a moving light source

First I will have to explain my question. Look at the image below. This shows doppler shift when an object is moving horizontally to the direction of the wave. Keep the word 'horizontally' in mind. ...
3
votes
1answer
378 views

Are black and white colours? [duplicate]

I am an artist, and I have heard that white is a 'tint' and black is a 'shade' in the artist world. I have also heard that they are colours in the normal world/scientific world. Which is correct and ...
0
votes
1answer
51 views

Effects of gravity on light [duplicate]

If gravity can bend light, why can't gravity slow light. At least momentarily? Wouldn't that give the illusion of the universe expansion speeding up?
0
votes
2answers
48 views

Image formation at surface of water

Consider a lake full of water which has an object immersed in it. Now, if an observer was at the surface at a sufficient distance so that the light ray from the object is internally reflected, should ...
6
votes
3answers
813 views

reflection at intersection of 2 mirrors

Consider 2 mirrors which intersect at an angle. If we draw a light ray intersecting the mirrors at their point of intersection, how will it reflect? What will be the normal at that point?
6
votes
1answer
51 views

Speed of light affecting appearance of galaxies viewed not face on?

So this has been really bugging me over the past few days (and forgive me if the answer is so simple). Let's say we're observing the Sombrero galaxy. It is about 29 million light years away and 50 ...
0
votes
1answer
23 views

scattering of light

How does the path of light become visible due to scaterring of light? According to me it will only tell the presence of colloidal particle but the book give the example of cinema hall projector and ...
-2
votes
2answers
56 views

Coexistence of light and dark

There are two things light and dark. Is there any system where the thing is neutral, i.e we see light and dark together in same ratio. Is it possible practically/theoretically ?
23
votes
5answers
4k views

Can the sun cast a shadow?

The sun's light can cast the shadow of another object, but does it ever cast its own shadow?
0
votes
2answers
66 views

How can opaque black object occur?

I know the fact that a material appeared as black when all wavelength photons were absorbed. I also know that opaque object is the result of reflection and scattering of light wave. Is it right? ...
3
votes
0answers
29 views

Does light escape from highly dense bodies [duplicate]

If it were possible to launch a projectile at the speed of light from a body with the mass equal to that of our sun but a density such that its escape velocity was the speed of light how far would it ...
1
vote
2answers
415 views

light penetration in the ocean

Is there an equation that describes the percentage of solar energy per wavelength that penetrates the ocean surface? For example, this website states that only 44.5% of the surface light reaches a ...
6
votes
3answers
546 views

How is temperature related to color?

I spent some time studying about temperatures and color of objects. It turns out that as we heat something it turns to red, then yellowish white and if we heat it more it turns to bluish-white. Like ...
0
votes
0answers
33 views

how does different colour wavelength intefere? [duplicate]

Say a red colour with 400nm mixes with blue colour with 700nm, but out of phase by a little. What would be the resultant colour? I would know how to represent the resulting wave mathematically, but ...
3
votes
4answers
513 views

What is difference between white objects and transparent objects as far as photons are concerned?

Transparent materials let photons through because the energy gap of electron is so large that the photons cannot be absorbed. If the material absorbs a photon, the photon disappears; does this mean ...
-2
votes
3answers
105 views

Could a photon travel faster than the speed of light in vacuum?

If the cosmic speed limit is the speed of light in vacuum, then what happens when a photon traveling through space meets gravity? Wouldn't gravity pull on the photon that's already traveling at max ...
2
votes
3answers
119 views

Young's Double Slit Experiment : What would happen if the “first slit” was too wide?

I was wondering what would happen to the fringe pattern displayed on the screen if the first slit (as shown in the picture), which is also known as "single slit", was made a bit wider. I read it in ...
13
votes
2answers
2k views

Why does one get an illusion as moon following him?

When you run or ride bike at night if you observe the moon you feel like he moves along with you as the same speed you are going. Why?
13
votes
9answers
4k views

Is darkness really light?

According to this wikipedia article "Consequently, most objects that absorb visible light reemit it as heat. So, although an object may appear dark, it is likely bright at a frequency that humans ...
3
votes
2answers
88 views

What does an analog voice transmission look like in the visible spectrum?

Analog radio signals are transmitted using light in the radio area of the spectrum. If it was transmitted using the visible spectrum instead (using a visible light emitting device instead of a radio ...
18
votes
1answer
1k views

Photobombing without app used by Harley Davidson

Here we see a photobombing trick, used by Harley Davidson. They achieve to incrust a logo on a photo you take. The logo is invisible with naked eyes and only revealed on the photo you take. How does ...
2
votes
1answer
50 views

Can a single photon induce current in a very small coil?

As I know from Lenz's law, I can induce current in a coil just by changing the magnetic field flux inside the coil. As I know from physics course, photons are electromagnetic waves (so they are the ...
0
votes
2answers
25 views

Wavelength of blue filtered light

Does blue filtered white light have a certain wavelength, or is this highly dependent on the filter and source of light?
11
votes
4answers
209 views

Does the speed of medium affect the path of light?

Let's say I shine a laser from a stationary medium into a moving medium (suppose the water is moving very quickly) perpendicular to the interface and back to a stationary medium like this: (Note: ...
6
votes
2answers
1k views

What would we see in the sky if it weren't blue

What would we see during the day when we look into the sky (other than clouds), if it weren't for Rayleigh scattering making the sky blue? Would the sky be dark, like at night?
1
vote
2answers
56 views

Does a light wave that has been cancelled by another light wave continue traveling forward?

I imagine that if a light wave is cancelled out by another light wave, it would still continue to exist as a photon that is traveling at the speed of light--only without a wavelength. Would it behave ...
-2
votes
5answers
100 views

Why does light travel in straight paths?

Why light travels in straight paths here on earth? What's the real cause that makes light photons to go in a straight line? and what are the factors that could change the path of light externally? ...
15
votes
7answers
2k views

Why do solar panels not have focusing mirrors?

Most of the solar panels that I have seen do not have any mirrors, etc., but usually solar cookers have mirrors. What is the reason for solar panels not having focusing mirrors?
1
vote
3answers
79 views

Is there an atomic level explanation for diffraction of light around opaque aperture?

It has always been a hard time understanding the phenomenon of diffraction of light around opaque objects. Hoe does it happen? Why does transparent objects do not diffract light? What quantum ...
0
votes
2answers
23 views

Snells Law: Does the k vector change on the boundary between mediums?

I was using Waves - Berkley Physics Volume III, and in explaining Snell's Law the author claims that as a wave is on the boundary between glass and air (going from glass to air) that the number of ...
1
vote
2answers
98 views

Why can't light waves bend? [duplicate]

Assume that you fixed a speaker to an inclined pipe as well the torch. You can hear sound from the other end of the pipe, but can't see the light from other end of the pipe, why?
0
votes
1answer
47 views

Given two surfaces, one that absorbs light and the other that reflects it, will there be a signficant temperature difference?

My likely wrong understanding of light is this: By some way the molecules are structured, a photon hits an atom or a structure, is absorbed, then re-emitted and it's that photon wavelength that I see ...
3
votes
1answer
63 views

Why do we see the sun's light color different from the moon's light color?

Why do we see the color of the sun's light as red or orange, while we see the moon's light as white, although it's reflected from the sun?
0
votes
1answer
66 views

relation between photon number and energy

Suppose there are two light beams. One is red while the other is violet. The energy of both is the same. Which one of these beams has a larger number of photons, or is the number of photons relevant? ...
1
vote
1answer
75 views

Physics and Skin Color: What differences do physicists observe between different skin colors?

I majored in social sciences, so I haven't taken a science class since 1999, so forgive me if I don't ask this right. What difference would skin color make from a physics perspective? Would there be ...
0
votes
1answer
46 views

speed of the light emitted from a fast moving object [duplicate]

Would not speed of the light emitted from the front of the fast moving object be the speed of light + the speed of the fast moving object?
4
votes
2answers
90 views

Is a Perfect/Lossless Mirror possible?

In traditional mirrors, some of the input light is absorbed by atoms in the mirrors surface and are 'lost' as heat, degrading the quality of the reflected image. Could this loss be compensated by an ...
10
votes
4answers
690 views

Why doesn't more light bounce off of things in the manner of sound?

If I'm sitting in the den with my door slightly cracked, I can hear my wife washing dishes in the kitchen down the hall. But why can't I also 'see' images of her washing dishes if, say, I looked up on ...
2
votes
1answer
56 views

Light Waves and Light Photons gedanken Experiment

Suppose you have a source of light that emits light with a wavelength of 2 meters, and you set the device to be turned on and switched off alternately. You also set it so that each interval the device ...
29
votes
9answers
6k views

Why can't we see gases?

I am not sure what causes gas molecules to be invisible.This question may look silly but I really want to know the story behind it.
2
votes
1answer
101 views

When photons are emitted, do they accelerate to reach the speed of light? [duplicate]

Photons are considered mass-less particle with a specific velocity but according to the electromagnetic theory, a photon is considered to have both energy and momentum. So what happen when they are ...
0
votes
2answers
93 views

What is the difference between light and visible light? [duplicate]

After watching a few videos on light and electromagnetic radiation, I am a little confused. The way things are explained, is that light is just the same as electromagnetic radiation I thought this ...
2
votes
0answers
56 views

Why does Pyrex glow orange under UV?

In a Physics lesson today our teacher performed a demonstration to show how quinine in tonic water glows blue when under UV light. He showed us the same demonstration using water in a Pyrex beaker, ...
177
votes
7answers
10k views

How does light bend around my finger tip?

When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry ...
2
votes
1answer
79 views

Relation between impact parameter and distance of closest approach of a light ray in Schwarzschild Geodesics

The following wikipedia articles are incompatible : Two body problem / bending of light by gravity Schwarzschild geodesics / bending of light by gravity According to both articles, the equation ...
2
votes
1answer
52 views

Why is a flower shaped diffraction occluder the best solution for controlling diffraction?

According to this TED talk by Jeremy Kasdin, Nasa is planning to spend $1bn on a "Starshade" project, where a giant flower shaped metal eclipser 20 meters wide is placed 50k kilometers in front of a ...
1
vote
3answers
115 views

About the speed of light and gravity

I read (I think ) that part of relativity theory is that a strong gravitational field distorts the uniform passage of time. If this is true and a lightwave 'travelling' to Earth passes a star near ...
0
votes
0answers
83 views

Calculate shadow path&size + object size based on distance

What are the variables I need to take in account if I want to calculate shadow path and size? I will try to simplify my questions. I have a $2D$ circle (radius: $28$) which means the size of the ...
1
vote
3answers
310 views

What happens to the index of refraction of a lens if placed in water?

What happens to the index of refraction and focal length of a lens that is initially in air that is then placed in water?
0
votes
2answers
44 views

Correlation between color of light visible to us and the intensity of transmitted light by the material

I wanted to know if there is any relation between the color of light observed by the eye and the intensity of light transmitted by a material. Let us assume that I have a table of intensities of light ...