Questions tagged [reflection]

This tag is for questions relating to reflection, the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. A familiar example of reflection comes from water waves; as the waves travel they reflect off objects that are floating in the water, and also reflect off the walls of the container holding the water.

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How does one apply the phase change of $π$ on reflection at the rigid end of a string?

Consider a string, with a free end $P$ and another end $Q$ which is rigidly fixed. Now, we start oscillating the point $P$ (with $0$ initial phase difference) and a wave starts traveling(in the ...
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3 answers
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How does a rainbow show all of its colours?

My question is tied closely to this one, asked a while back on the website. As far as my understanding goes, a rainbow is formed by sunlight undergoing two refractions and a reflection inside ...
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6 votes
2 answers
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Dropping a mirror into a blackhole

Say you dropped a mirror into a black hole while observing at a distance and holding a clock such that the clock's face was pointing to the black hole. What is the latest time you would view on the ...
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Why does an antinode form at the open end of an organ pipe?

I recently learnt about reflection of waves in various media and the resultant standing waves formed. In a string which is tied at an end, the wave formed reflects with a phase difference of 180 (at ...
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2 votes
1 answer
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How is this circular pattern of a streetlantarn behind a tree formed?

A few months ago, while walking the dog at night, I noticed a strange effect. The streetlight shining behind a barren winter tree, was somehow changed, by reflection from the branches, showed a ...
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Why is the angle of incidence equal to angle of reflection? [duplicate]

This is true experimentally, but how do I prove this?
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Mirror Equation for convex mirror

Question: I have a convex lens with focal length $\mathrm{70mm}$ and it's forming a real image. We have a virtual object at $\mathrm{90mm}$ to the right of the mirror. Using the mirror equation gives ...
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3 answers
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Why image of vertical object is always a straight line and perpendicular to principal axis?

I am a high school student and I am very confused in geometrical optics, In all textbooks the mirror formula is derived by already assuming that the image of any vertical object (perpendicular to the ...
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1 answer
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Concave mirror and convex mirror placed facing each other [closed]

A convex mirror in a concave mirror each of focal length f are placed coaxially. They are separated by 4f and their reflecting surfaces face each other. A point object is kept on the principle axis at ...
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Symmetry relations of a Hamiltonian (Mirror, Chiral, Inversion, Rotation)

I'm reading a paper https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.235136. Regarding Eq. (4)~(6), I have the following questions: (A) Eq. (5) shows a mirror symmetry relation $M_z H \left( ...
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What is the theoretical range of temperature the air must be in order to reflect/refract light (for a volumetric display)?

Well, the only question I found in this website about volumetric displays on air was this one, but it specifically suggests making air denser in order to make it work, but my question is specifically ...
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4 votes
5 answers
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If particles are also waves cant we invert them by making it reflect off a fixed boundary?

When a pulse on a rope gets reflected off a fixed boundary, it phase shifts 180° and inverts itselfs. If particles are also waves, will doing an equivalent thing create antiparticles? Is it possible ...
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3 votes
1 answer
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Sunscreen protection, SPF, and amount applied: relationship?

In the article How SPF Changes with How Much Sunscreen You Use (last updated Dec 29, 2017), the author says that it is disturbing that insufficient sunscreen (in theory) decreases protection ...
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4 votes
2 answers
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Rainbow reflections from salt crystals

Especially on a sunny day in the winter or spring, I often notice faint rainbows when I look down at the edge of the road by the curb. I am not sure what causes these rainbows, but I believe that ...
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0 votes
2 answers
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What is the smallest value of the incident angle in Bragg's law?

The title of my question basically is what I want to know. In Bragg's law, $nλ = 2 d \sin{\theta}$, if we want to find, let's say, $d$, and know only $\lambda$ and $n$, but not $\theta$, what could be ...
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Definition of transmission and reflection coefficients for a particle

Quick intro: A 1D quantum particle is subject to the potential $$ V(x) = \begin{cases} 0 \;\;\;\;\; x\leq 0\\ V_0 \;\;\; x > 0 \end{cases} $$ I am trying to understand the definition of ...
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Image formation by a concave mirror-

I have read that concave mirrors are converging mirrors so they form a real image . Real images are inverted and they are always obtained on screen. Then why we see the image formed by the concave ...
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8 votes
2 answers
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Why does diffracted light in certain TVs get collimated in six straight or curved rays? [duplicate]

This evening, looking at the television in my apartment, I noticed that the light reflected on it manifested some kind of regular pattern. When the source of light is sufficiently far, this consists ...
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1 answer
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How about optical fiber without cladding and directly coated?

How about optical fiber without cladding and directly coated? I have got some answers from here, but how about optical fiber without cladding and directly coated? and the coating material have a ...
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1 vote
0 answers
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Can I use all 4 sides of a polarizing beamsplitter cube as inputs?

The polarizing beamsplitter cube on the following diagram splits non-polarized light in the input a into 2 orthogonal polarizations: p-polarized light is transmitted into the output c while s-...
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What causes the mirror image of my finger in a spoon to flip when I put it closer?

When my finger is far away, its image is flipped: But when I move it closer, it's not flipped: What causes the flip? According to the illustration of this answer, it flips when the object moves ...
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How to convert absorbance light into reflectance from a semi-spherical surface

Like the name of this question says I would like to know how to convert the light absorbance data into reflectance. For instance my diagram looks like the picture below, where I have an incoming light ...
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-1 votes
1 answer
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Can a polarized light be reflected?

First of all, this question is NOT about what happens to an unpolarized light when it is reflected by a surface. This question is already well answered by the web and is not my current concern. I am ...
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2 votes
1 answer
221 views

Reflectance and transmittance from an anisotropic layer

I am trying to follow a derivation for the reflectance and transmittance of a plane wave from an anisotropic material ($\varepsilon_a,\varepsilon_b,\varepsilon_c$). The derivation uses a $4 \times 4$ ...
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2 votes
1 answer
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We know that a concave mirror always form either real and inverted images or virtual and erect but i can't understand what is happening here

For a real object, a concave mirror always forms real and inverted images when object is between infinity and focus and forms virtual and erect when object is between focus and pole , but in the ...
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2 votes
1 answer
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If Plane Mirrors form only virtual images, why can I obtain the real image of a laser beam that I shone on the Plane Mirror?

I thought about this, and couldn't really come up with a suitable explanation.
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Why do these lace threads reflect light in this way?

I was watching a video about the making of leavers lace and came across this. I'm wondering why the threads reflect the light as seen in the picture. How does that work? I took a screenshot from this ...
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2 answers
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How does light interact with the whole surface without the angles of reflection and incidence being equal?

Suppose we have a light source shining all over the surface , and there is a photon detector separated by a block Q . I would expect it to have only one line at the center the center , where the angle ...
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1 vote
0 answers
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What's the reflectance of common white objects

Let's say I have a point light source which emits in the range 440nm-630nm uniformly distributed light on a recently polar white painted wall or a piece of office paper. What's the reflectance in ...
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0 votes
1 answer
35 views

Do Virtual Objects always Produce Real Images?

If we place two plane mirrors facing each other wouldn't the image produced by the first mirror act as a virtual object to the second mirror? If so, would the image produced by the second mirror then ...
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0 votes
2 answers
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Why solar flux concentrators can achive only $\rm 1500°C$ of temperature if Sun temperature is $\rm 5500°C$?

Why solar flux concentrators can achive only $\rm 1500°C$ of temperature if sun temperature is $\rm 5500°C$ ? If it is possible to concentrate a flux from a parabolic mirror of area $\rm 400\ m^2$ to ...
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0 answers
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How does reflection polarise light on the atomic level?

From my reading when light is reflected S-p polarisation occurs with the reflected light being parallel to the surface in polarisation and the mixed light being transmitted through. Light is absorbed, ...
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6 votes
2 answers
494 views

Why does plane mirror form image of same size as object?

Plane mirror form images of the same size as of the object. Also if we need to see ourselves completely in mirror, we would require a mirror of at least half out height. Assume I am 6 feet tall then ...
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How does reflection of light work on an atomic scale? [duplicate]

Let's say white light is incident on an orange. It absorbs wavelengths via the excitation of the atoms within the molecule that gives it pigment, but how do these molecules reflect that orange ...
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0 votes
1 answer
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Having trouble understanding light absorption versus reflection

Do the atoms within a material absorb the photons and re-emit them in the direction they came back from (similar to atomic emission spectra, but slightly different because this involves hybridization ...
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2 votes
1 answer
77 views

Why do mechanical waves reflect at a boundary?

I am trying to better understand why mechanical waves, primarily longitudinal acoustic waves, reflect at a boundary. I am currently understanding that, for all waves, variation in media ...
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1 vote
1 answer
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Reflection at asymmetrically shaped refractive-index profile

Hi. I have a question on reciprocity in optical reflection. We have a refractive index profile (as a function of x) that continuously varies (Figure). At x=-inf and +inf, n = n1. Around x=0, the ...
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2 votes
1 answer
62 views

What colour are metals? [duplicate]

I know that glass is actually green in that mirrors will always leave a green tint. This is because, although it's a small margin, green is the most absorbed wavelength for glass. Following on from ...
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Beatings from a radar wave and plane velocity

Suppose a radar is emitting a spherical wave with some wavelength $\lambda$ and there is a plane traveling with velocity $\vec{v}$ towards the radar (and assuming plane waves getting to the plane). I ...
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1 vote
1 answer
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What does it mean when we say there is a phase change of $\pi$ when waves are reflected off a rigid surface?

Suppose we describe a wave travelling along at positive $x$ axis, using $y_1=a\sin(\omega t-kx).$ Suppose, at $x=0$, we have a rigid boundary, such that the wave is reflected. Let us write this ...
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0 votes
1 answer
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Calculating photographic exposure - confused about luminance, illuminance, luminosity etc

On first glance this sounds like a photography SE question, but it's more concerned with physical measurement of luminosity, luminance etc - the photographic application of the value calculated is ...
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2 votes
1 answer
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When measuring IR for temperature of shiny surfaces, how is the object own emission added to the reflection?

While discussing measuring temperature of a heated glass plate used in 3D printers, it was pointed out that IR thermometers are not accurate because, for uncoated and shiny glass surface, they measure ...
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How much can we enlarge the picture of a distant galaxy by this method?

If reflection is used instead of refraction and if the curved mirror is highly reflective and cast the image of the galaxy in a obscure chember on a relatively distant screen how much the image can be ...
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0 votes
1 answer
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Can crooked surfaces alter speed messurement using a laser?

this might be an unconventional question yet I think the physics community would be the one to help here. Please hear me out. So my problem/question: I drove into a laser speed trap with my motorcycle ...
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-3 votes
4 answers
103 views

What is a rainbow?

What is a rainbow? I've read that an image is formed when light rays after reflection meet. So in case of a rainbow when light ray after refraction by the water droplet reaches our eye than wouldn't ...
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0 votes
0 answers
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Total Internal reflection and law of reflection

Does the 2nd law of reflection (i.e angle of incidence equal to angle of reflection) holds for total internal reflection?
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Is there any physical interpretation of the refracted light in the case of total internal reflection?

In the case of total internal reflection trying to obtain the angle of refraction leads to a value which cannot be represented as a real value. $$ \sin(\theta_t) = \frac{n_1}{n_2}\sin(\theta_i) \qquad\...
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0 votes
1 answer
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Alternative Schlieren parabolic mirror configuration

I have sourced two parabolic mirrors and am planning to set up a Schlieren for ultrasonic visualization and future fluids projects. A very common dual parabolic mirror configuration is the Z-type, ...
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15 votes
6 answers
9k views

If diverging rays never meet, why do parallel rays meet at infinity?

I've seen that in the case of concave mirrors if the object is between focus and the pole - the reflected rays diverge and never meet. But if the object is at the focus, it's defined to be meeting at ...
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1 vote
2 answers
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What would happen if light hit a non-differentiable curve?

Suppose we are talking about reflections in 2D, and let's suppose that hypothetically I have something like a weistrass function with one side completely reflective How would light reflect of it's ...
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