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Questions tagged [reflection]

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50
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2answers
7k views

Why are gold mirrors yellow?

Why are golden mirrors yellow? Do they add a yellow component to the spectrum or absorb non-yellow components? If they absorb, then why are they used in telescopes being imperfect? If they add a ...
33
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6answers
17k views

Why did high quality mirrors use aluminum coatings instead of silver?

I have two questions on mirrors. I’ve read that in the past quality mirrors were coated with silver but that today vacuum evaporated coatings of aluminum are the accepted standard. When I look at the ...
14
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6answers
7k views

How come an anti-reflective coating makes glass *more* transparent?

The book I'm reading about optics says that an anti-reflective film applied on glass* makes the glass more transparent, because the air→film and film→glass reflected waves (originated from a paraxial ...
10
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1answer
492 views

Reflectivity of a glowing-hot metal surface

When a polished piece of metal (or steel in particular) is heated to incandescence, how do its reflective properties change? Given a mirror-like surface, would the object temporarily cease to act ...
12
votes
3answers
2k views

Using a naked black hole as a mirror?

http://www.youtube.com/watch?v=ENd8Sz0AFOk The YouTube video is a good example how the gravity of this merging binary black holes bend light around themselves.
6
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2answers
407 views

About photons and mirrors

If a photon hits a 'perfect' mirror (with no environment interference) would the mirror move a bit?
2
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2answers
6k views

Huygens' Principle During Reflection: comparing wavelets from before reflection with wavelets from during reflection

I was recently reviewing geometric optics, during which I read about Huygens' Principle and how it could be used to prove the Law of Reflection from the "light is a wave" viewpoint. I'll quote what I ...
2
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4answers
8k views

Can light be trapped theoretically?

My question is a little silly I know, but I'm curious to know if a particle of light can be theoretically trapped between two reflective screens. For example once the particle of light has left it's ...
4
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2answers
3k views

How can a green laser be reflected as orange?

My friend recently bought a high-powerd pocket laser pen (from China). It is green, and reflects off most surfaces as green. On some orange surfaces, it reflects orange instead. That is to say, we ...
3
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0answers
188 views

Are there Optical Magnetic Mirrors (OMMs) which reflect via interaction with the magnetic field?

The most familiar mirror relies on reflection from a metal, where the very strong interaction of the electric field component of the EM wave with the conduction electrons produces a reflected wave. ...
5
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1answer
831 views

Evanescent wave coupling

In my optics course we have observed that in several applications, such as prism coupling of modes in an optical waveguide, coupling between two waveguides, attenuated total internal reflection (or ...
5
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2answers
6k views

Fermat's principle to prove the law of reflection

Fermat's principle tells that a light ray will follow a path from point $A$ to point $B$ so that the optical path length of this path is an extremum over neighboring paths. I wanted to use this ...
3
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3answers
1k views

How to understand the symmetry $\Sigma^-$ in the wavefunction of a diatomic molecule?

In Wikipedia (and elsewhere), a particular symmetry of the quantum system of a diatomic molecule is mentioned: symmetry under reflection along a plane containing the internuclear axis. The ...
11
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1answer
12k views

Why do some materials reflect (metals) and other materials reflect and refract (glass) from the quantum perspective?

Recently I was asked to explain the difference between reflection and total internal reflection from a purely conceptual standpoint (no math). Let me explain what I already know. Reflection and ...
8
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1answer
5k views

Why does the light at the bottom of the pool form this awesome pattern?

Take a look at the following picture: Why does the light at the bottom of the water form this pattern? I have also seen the same phenomenon in all the swimming pools I've ever visited, of whatever ...
1
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2answers
6k views

Rainbow reflected on TV screen? (pic attached) [duplicate]

According to wikipedia, A rainbow is an optical and meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets... Given that we require ...
3
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3answers
2k views

Why don't E&M fields change orientation after hitting a surface?

In essentially every derivation of the Fresnel equations, the general problem of radiation hitting a surface at a certain angle is broken into two parts (out of which we hope the solution any general ...
1
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1answer
327 views

Explanation of $\sin(\theta) > 1$ for total internal reflection

Reading about total internal reflection, and I understand that it occurs when the sine of the refracted angle is greater than 1. What I don't see is how you ever have a $\sin \theta > 1$. Jackson ...
15
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2answers
9k views

Why is reflected light polarised?

Why is reflected light polarised? I have learnt about Brewster's angle, and how at a particular angle all light reflected is polarised, but do not understand why. Is this something that could be ...
4
votes
2answers
26k views

Why does your reflection suddenly turn upside down while slowly walking away from a curved mirror?

Many people should have realised, when looking into a concave curved mirror (or even a rather reflective spoon in that fact) at a close distance, you will see a slightly distorted reflection. But as ...
4
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2answers
143 views

How is it possible that multiple overtones can exist at the same time?

I was wondering how it is possible for overtones to co-exist at the same time. When one pulls a string, it starts to oscillate and forms a standing wave with frequency $$f_0 = f$$ Additionally, ...
4
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4answers
1k views

Shining a laser onto a mirror

Theoretically, if I shined a laser at a mirror at an angle of 0 degrees so that the light was perfectly reflected back to the light source, then I should not be able to see the light because it is not ...
3
votes
1answer
635 views

computing wavefront deviations for off-axis mirrors

Suppose you have two off-axis aligned mirrors which are nearly planar, with small deformations such that a wavefront at plane $P_I$ at distance $-D$ from the mirrors, is refocused at distance $D$ at ...
3
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1answer
255 views

How does one calculate the polarization state of random light after total internal reflection

How does one calculate the polarization state of random light after having been totally reflected by a single dielectric interface? Please consider pure specular reflexions from a plane interface ...
1
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1answer
2k views

Why is a rainbow curved in shape?

Why is a rainbow curved in shape? When dispersion of light takes place, light splits into seven colors, but when rainbow is formed it appear to be bent. Why does this happen even though light travels ...
1
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2answers
1k views

Reflectivity with complex refraction indices

So the general equation for the reflectivity at the interface between two materials is given by: $$R=\left(\frac{n_1-n_2}{n_1+n_2}\right)^2$$ in case of air/glass $n$ is real, but for, say, ...
1
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1answer
2k views

Why do we see an inverted image in a spoon when kept far from our face with concave side towards our face?

We see a virtual inverted image whereas in case of concave mirror we can see a virtual image which is erect.
1
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1answer
2k views

Inside a spherical mirror

imagine standing inside a sphere composed entirely of mirror surface; what does this look like? inside is lit by an invisible light source if each point encounters a reflection of itself, what is ...
0
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1answer
272 views

Why do Lambertian Reflectors Privilege the Observer?

Lambert's Cosine Law for Lambertian Reflectors states that the radiant intensity $I$ (watts per square meter per steradian) of reflected light as a function of the angle $\theta$ from the normal to ...
11
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1answer
575 views

QM: why is reflection of a photon not a measurement?

Many experiments with entangled photons are sending them through different glass fiber cables (e.g. in opposite directions for spatial separation). The photons will inevitably be reflected many times ...
4
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3answers
7k views

What “exactly” happens when a ray is incident at the critical angle?

The question arose when my physics teacher taught me geometrical optics and told that the phenomenon of both refraction and $reflection$ occur by change in medium. First of all, I'm not sure about the ...
3
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1answer
496 views

Deep confusion with conventions and signs in geometric optics

This is an equation given in my book. The question is why have they used a negative sign on the LHS? Now, if you try to derive the mirror equation with simple geometry, you get 1/v +1/u =1/f . I ...
2
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3answers
3k views

Is white a single color? [duplicate]

We have seen the Newton disc, when it is rotated it produces white color. So I want to know whether white exists as a single color or is that a combination of multiple colors?
2
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2answers
54k views

Does more reflective aluminum foil make a room cooler compared to less reflective foil?

Aluminum foil is said to be not absorbing light at all. It reflects light. So, does it mean that a more shiny aluminum foil will reflect more light and thus make the room more cooler as compared to ...
1
vote
1answer
821 views

Wave reflection, boundary conditions?

When a wave-pulse is reflected such that initially it was moving in the denser medium, and towards the other side of the interface lay the rarer medium, will there have been a phase change post ...
1
vote
1answer
428 views

Why light rays gets scattered when it enters a translucent window pane?

Consider the light source is the light post, outside the window of my house (Pic 1). When the rays from the light post enters through the window pane which is translucent gets scattered and forms a ...
1
vote
1answer
378 views

What really is reflection? [duplicate]

What really is reflection? Is it just the reemission of EMR? I asked my teacher, he said in quantum sense, it is true. But when I read something about emissivity in Stefan Boltzmann's equation, it ...
0
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1answer
4k views

How to calculate a straight edge diffraction pattern

A straight edge diffraction pattern is not the same as a slit or multiple slit diffraction pattern. The spacing between fringes is not equal but gradually gets smaller the farther out you go as in the ...
0
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4answers
16k views

Is there a substance that doesn't reflect OR absorb light from the visible light spectrum?

Is there a substance that doesn't reflect or absorb visible light but may reflect light from another spectrum? Is there a theoretical substance that would have these properties? EDIT: Sorry I wasn't ...
0
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2answers
10k views

reflection at speed of light when both mirror and viewer is travelling at the speed of light [duplicate]

consider me sitting on the top of a train which is travelling close to the speed of light, will I be able to see my image on a mirror which I'm holding in my hand??
0
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2answers
394 views

For the derivation of the form of a paraboloidal reflector, there is much more in need as just Fermats principle?

I am currently learning about Optics using an MIT OpenCourseWare Course. I have in particular a question about the application of Fermat's principle in Lecture 3, i.e. deriving the shapes of parabolic ...
0
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1answer
1k views

How are these balls reflected after they hit each other? [duplicate]

Possible Duplicate: Physics of simple collisions I have 2 photos of the balls, one before the collision and one after the collision. They do a elastic collision. I want to know how is the ...
0
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2answers
393 views

Solar Sail Questions

I'm just looking for a good (better) analogy. How do massless photons put pressure on a surface especially when it's a mirror? Using the analogy of the wind (atmosphere) on a sail breaks down when I ...
76
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1answer
7k views

Why does soaking a fabric make it more transparent?

It's a well-known fact that when one soaks a thin piece of fabric, it will often become more transparent than it was before. What is the reason behind this? I can't put glass behind the fabric and ...
42
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3answers
8k views

Why does a mirror reflect visible light but not gamma rays?

Visible light (~500 THz) as well as gamma rays (~100 EHz) are electromagnetic radiation but we can reflect visible light using a glass mirror but not gamma rays. Why is that?
18
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7answers
6k views

Can light continue without a light source? [duplicate]

If you have 2 mirrors over for each other placed exactly so they face each other perfectly, and then use a laser light pen as the source into one of the mirrors so it bounces to the other mirror and ...
8
votes
6answers
12k views

Why does light reflect more intensely when it hits a surface at a large angle?

I mean, what is happening at a microscopic level to cause this behavior? Here's what I got from Wikipedia: On Reflection (physics)#Reflection of light it says that "solving Maxwell's equations for a ...
8
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3answers
8k views

How can I determine transmission/reflection coefficients for light?

When light rays reflect off a boundary between two materials with different indices of refraction, a lot of the sources I've seen (recently) don't discuss the relation between the amplitude (or ...
1
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3answers
3k views

Question about intensity of EM waves

For electromagnetic wave if it's reflected from a perfect conductor standing wave can be form. I wonder why Poynting vector can be used to describe the intensity of standing EM wave. (see p.19 of http:...
9
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2answers
1k views

Is reflection instantaneous?

I was wondering while reading "On the Electrodynamics of moving bodies" by Albert Einstein (1905) (Translated to English). In the paper, he describes the time as being: by definition that the “...