Questions tagged [visible-light]

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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Is light a single wave when we refer to frequency?

When we say that light oscillates $n$ times (frequency) in a second do we mean that the same electromagnetic field travelling through space oscillates $n$ time's? As i have seen diagrams suggesting ...
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3answers
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How does change in Temperature affect Refractive Index/Optical Density of a medium?

In my school book its stated that: With increase in temperature, the speed of light in a medium increases, so the refractive index of medium decreases. I read in another answer that: Refractive ...
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What is Energy? Like, seriously, what is it? [duplicate]

Here's a question that's been on my mind for quite some time now. What the actual hell is energy? Like, seriously. I understand real-life is nothing like fiction where characters and machines can ...
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How does light from distant galaxies reach us?

Why doesn’t a ray of light which is emitted by a distant galaxy, say about a thousand light years away, die down in between? I mean, how do the light rays from different galaxies so far away reach us ...
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Mach-Zender Interferometer with an external Phase shifter

On passing a input beam of form $\begin{pmatrix} { \alpha\\ \beta} \end{pmatrix}$ through a Mach-Zender interferometer with a phase-shifter of phase $\delta$ on either lower leg or upper leg of the ...
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If a star gravity can change the apparent location of another star on the sky, can it change the gravitational field vector of that star?

If a star gravity can change the apparent location of another star on the sky can it change the gravitational field vector of the second star? In simple words if a star gravity deflects the position ...
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The detection and measurement of the ultra-yellow and infra-cyan in an inverted spectrum [closed]

The detection and measurement of an inverted spectrum including the infra-cyan and ultra-yellow beyond the visible range is, in my estimation, one of the most important observations in physics in the ...
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1answer
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Scattering of light by gas molecules in Atmosphere, responsible for sky's blue color? [duplicate]

What do we mean when we say gas molecules in air scatter sun light (more blue)? Do they reflect sunlight? Is beam of sunlight falling on one molecule and each rays got reflected into different random ...
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1answer
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Why Earth is viewed crescent from moon when the Earth is experiencing total solar eclipse?

Suppose a person, let's say Neil, is on moon and Earth is experiencing a total solar eclipse so how should Neil perceive the Earth? This is also a question from KVPY (5/11/2017) question no. 22. as ...
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1answer
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How is light affecting the weight of different colored objects?

I was told here that light can move an object and that it pushed against it. Lets say I have objects of the colors Red, Green, Blue, Yellow, Magenta and Cyan, each placed on different balances that ...
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Can something be moved with light?

I was having the idea that light was probably something that had mass and could push something. I looked it up to find that it does not weight anything. Then again, I wonder if you could push ...
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1answer
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What is scattering of light?

What actually we mean when we say scattering of light by a particle? Is a ray of light on being by scattered by a particle get divided into many sub rays that scattered in different direction ? Or A ...
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1answer
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Are there an infinite or finite number of colors (can we see infinity?) [closed]

Take any blue or red, mix in equal parts and you have purple. Now mix 50 units of red and add 25 units of blue for another purple, then 50 units of red and 12.5 units of blue for yet another purple ...
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1answer
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Is colour different when observed in different medium [duplicate]

A diver is inside a swimming pool. What colour would he observe inside the pool if a light source of green colour is kept outside the pool. My textbook says that he observes blue colour. But I think ...
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1answer
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Is it possible to create light only from a changing current in a wire?

A changing current in a wire creates an electromagnetic field. Light can be considered an electromagnetic wave, so my question is: would it be theoretically possible to create visible light by ...
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1answer
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What type of lenses or a combination of optics do I need to reduce a flashlight beam size?

Optics is not my best subject. I know the basics of how light behaves as it go through a lens. I tried to understand further but got more confused as I get deeper into this subject. My goal is to make ...
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1answer
81 views

Distinguishing between different types of elliptical polarization

How to distinguish between a mixture of plane polarized and unpolarized light, and a mixture of elliptically polarized and unpolarized light? When we pass plane polarized wave though quarter wave ...
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1answer
59 views

Are photons countable/uncountable? Lebesgue measure, probability

I have a question which is bugging me for a few days now (I'm a math major but I took no physics courses). I am probably not the first person to come up with such question, so I would appreciate any ...
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1answer
27 views

Relative motion between a light source and a stationary observer

I've been taught that for a stationary observer moving at constant relative velocity away from a light source, this light source will decrease in frequency as the distance between the two increases. I ...
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4answers
151 views

Why is it said that, because gravity can bend light, that this entails a curvature of space-time?

Why can't gravity affect light directly without any reference to space-time? How does light bending show that space-time is curved? I would have thought that it shows that massless particles are ...
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2answers
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Reflected light and color fade [duplicate]

The color of many objects fade with constant sunlight. Is the reflected light "leaching" the color, is it carrying something substantial away? What is expending the color? This is not about ...
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1answer
66 views

What keeps a light wave 'waving'? [closed]

Why does the a light wave crest, rather than continuing off in the direction it's heading prior to the moment it begins cresting? What force/acceleration/thing 'turns' the wave towards the bottom (or ...
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1answer
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Is there a "water wave" analogy for lasers?

I've been trying to understand why light can both be a wave and travel in a straight line, and a lot of the answers seem to include reference to the fact that the wavelength of visible light is ...
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1answer
55 views

Will I be able to see a light coming from a laser in the edge of the universe?

It is said that light's intensity decreases with increase in distance. Suppose if there is a laser in complete vacuum, emitting a collimated light beam from one end of the universe for about 93 ...
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1answer
35 views

What happens if a light source is present on both sides of a 1-way glass?

My question is that if there is a light source on both sides of a dual-sided mirror (the ones where form one side it acts like a mirror and the other like transparent glass), what would happen?
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2answers
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Question about refraction in a swimming pool

When you are at the bottom of a swimming pool with lane lines at the bottom of the pool, you can see the lane lines at the surface of the pool as well. Can someone explain why this occurs? I know it ...
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1answer
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What would physics look like if light were not constant in all reference frames? [closed]

Is there a more fundamental theory that explains why speed of light must be constant in all reference frames? This seems like such a huge premise but I've never heard why it must be true, only that it ...
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1answer
90 views

What happens to light ray moving from one transparent medium to other at the angle of incidence $90^{\circ}$?

I think when a light ray moves from one transparent medium towards other at $90^{\circ}$ incidence angle,it will not suffer refraction but continue to move indefinitely in the initial medium. But, if ...
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2answers
185 views

Why does sunset spread over the horizon?

Why does sunset light spread horizontally over the horizon, instead of being radially spread around the solar disk? I understand physics about refraction, and wavelength, and gradient difference ...
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2answers
27 views

What causes the diffuse reflection of an object onto a nearby object to be colored the same color as that of the object?

Assuming a light source, emitting white light,a red colored diffuse sphere lit up by the light, and a white plane below the sphere acting as the 'floor', we find the diffuse reflection of the sphere ...
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1answer
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Pattern of light formed when a wire is placed in front of a laser

I'm a high-school student. I recently recreated the double slit experiment myself with the help of a laser pointer, using wire and black tape to create the two slits. When disassembling the apparatus, ...
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2answers
71 views

What is the wavelength of white light? [closed]

Does white light have a wavelength, and I know that the sun emits white light, but the atmosphere makes it refract to make it appear yellow to us. Do all the stars in the universe emit white light?
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3answers
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Microscope and dual nature of light

Does a light microscope also prove the particle nature of light? As in electron microscope there is either transmission or absorbance of electrons to create an image, hence the question above!
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2answers
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Photoelectric effect with high frequency and low intensity of light [closed]

What happens to the number of photons striking the free electrons on metal surface with high frequency and low intensity of light? High and low intensity of light of photons to electron on metal ...
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1answer
31 views

Laws for light absorbtion

When light of one particular wavelength is directed to a surface, it may get completely or partly reflected, or completely absorbed. Is the amount of reflected light always proportional to the ...
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1answer
37 views

Reflectance and Reflectance Color of Metals

I do not understand the layman's physics behind the reflectance curve of a metal based on the complex index of refraction. Figure 24 from Background: Physics and Math of Shading by Naty Hoffman graphs ...
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1answer
34 views

Why refractive index of same material is different for different monochromatic lights?

Yeah I know that refractive index is different for different monohromatic lights due to the change in velocity of light. And as frequency doesn't changes and only wavelength changes while travelling ...
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1answer
42 views

Photon irradiance and solid angles

A blackbody is in equilibrium with a radiation field at $\nu$ when $$ I(\nu)=\frac{8 \pi \nu^{2} }{ c^{2}}\left(\frac{1}{e^{h \nu / k T}-1}\right) $$ where $T$ is the temperature of the blackbody and $...
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1answer
49 views

Light: reflection and transmission

When white light hits a thin "transparent material", is there a general relationship between the spectra of the reflected and transmitted components? For example, do red filters (that make ...
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0answers
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Why is it possible to couple multiple wavelengths into a single mode optical fiber?

I'm quite new to the mode theory, but as I understand, single mode fiber should only allow a single pattern of wavelength + polarization. I'm assuming a non-modulated non-coherent light (a white LED, ...
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4answers
62 views

Electron wavelength vs. light(s) wavelengths

I am doing some research into wave and waveform. I am looking at different types of microscopy for potential purchase. However, I came across Max Knoll a minute ago and I am curious as to how ...
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1answer
116 views

What is the maximum possible temperature of a 1mx1mx1m cube that is the focal point of an array of mirror reflected, concentrated beams of sunlight? [duplicate]

If we assume an array of 1m x 1m mirrors reflecting sunlight in an Alabama field to a common point, what would be the maximum possible temperature that could be reached? How many mirrors in this ...
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1answer
27 views

How does conservation of energy fit in with an object absorbing visible light rays but emitting IR rays?

When an object absorbs visible light (such as from the sun) it gains a certain amount of energy. Most objects then emit back IR radiation (without emitting back any visible light) which has a lower ...
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42 views

Light and electromagnetic waves

Light has no charge and electromagnetic waves are created by charged particles, then how does light create an electromagnetic wave?
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Speed of electromagnetic waves in vacuum [duplicate]

Why is the speed of all electromagnetic waves the same in vacuum? Please try to explain in a simple manner.
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34 views

How effective are privacy screens at blocking blue light in the presence of other protective measures?

For quite a while, I've been using privacy screens, which not only increase... well, privacy, but also purportedly block blue light. However, web search results generally yield very broad statements ...
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1answer
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X-Rays and UV Penetration Dichotomy Relative to Visible Light (Shorter Wavelength but opposite penetration)

My understanding was that relative to visible light, ultraviolet tends to be more strongly absorbed by materials because the higher energy photons are likely to be able to interact with the material. ...
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58 views

How to make a room completely dark? [closed]

Im going to do a dark room retreat for myself where I will stay in a dark room for 40days which has a lot of physical, mental and spiritual benefits. Now about how to make my room completely dark? I ...
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1answer
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Are the photons in a standing wave moving at $c$?

So, in a standing wave, two superimposed waves produce a wave that remains stationary, with its particles resonating back and forth, right? For instance, in a water wave, two waves moving in opposite ...
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Reflection of light at a quantum level [duplicate]

In Richard Feynman's book 'QED' he says that light when reflected of a mirror it has an amplitude to travel every way possible to a second point (P) and not just from the center like described in ...

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