Optics is the study of light, and its interaction with matter. It includes topics such as imaging systems, fiber optics, lasers, quantum optics, and more.
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1answer
386 views
How to read a lens spot diagram?
I would like to get an explanation on how to understand such a lens spot diagram:
Thanks
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0answers
33 views
Smaller Airy disk with another lens?
Is it possible to reduce the airy disk size produced by one lens with another lens placed after the previous one? For example, parallel ray incident on first lens L1 (without aberration), then there ...
3
votes
2answers
70 views
Why is $\vec j\cdot \vec e$ the joule dissipation?
I always see $\vec j\cdot \vec e$ as Joule's dissipation and I don't understand why. For example, if we have a uniform electric field $\vec e=e_o\vec u_x$ and we release an electron in it, it will ...
-1
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1answer
84 views
Funny classroom experiments [closed]
I'd like to perform some weekly classroom experiments to keep my students interested and curious about everyday physics. Those experiments have to be quite easy to set up and not too easy to ...
0
votes
2answers
71 views
the possibilty of that detuned laser can excite an atom? if yes how?
I am not sure about the possibility if detuned laser can excite an atom? if yes what is the explanation?
3
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2answers
515 views
How do head mounted displays simulate infinite focus?
First, when I say infinite focus, I am using the term from photography, perhaps incorrectly. Secondly, I believe am not talking about convergence, but about focus. If I am not mistaken, with ...
1
vote
3answers
40 views
Trapping EM radiation
Is there a material which can allow light (or any other EM radiation) to pass through from one side as if it is transparent but its other side reflects light like a mirror?
0
votes
1answer
75 views
Seeing a mirage through mirror?
Okay, I am not really good in physics (rather terrible), but nonetheless.
So, I was just wondering if you can see a mirage, is there something special in our eyes that we can see it or what? I mean, ...
1
vote
0answers
111 views
How does a Fresnel rhomb work (half and quarter wave plate)?
How does a Fresnel rhomb work (half and quarter wave plate)?
I am aware of birefringence, which creates a phase shift of $\Delta\phi=\dfrac{2\pi\Delta nL}{\lambda_0}$. But this doesn't explain how a ...
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0answers
9 views
Image formation [duplicate]
What is the real cause behind the formation of an image? It is explained as" when rays of light focus at a point image is formed." So here we have two events, one focusing of light and another ...
4
votes
2answers
828 views
Make a semi transparent mirror with copper
The question:
How would you make a semi transparent mirror (50% reflection, 50% transmission) with glass with a layer of copper. For light $\lambda$ = 500nm Try to be as realistic as possible
What ...
1
vote
1answer
76 views
Is this mental picture of photon correct?
What is exactly meant by a statement like "there are about 400 photons per cubic cm in certain region"? Should I mentally picture this as 400 discrete photons enclosed in that volume, each moving at ...
0
votes
1answer
43 views
Circular polarisation
If we have a planar and harmonic EM wave, with $B$ field:
$$B=A\left(\begin{array}{c}
1\\
i\\0
\end{array}
\right)e^{-i(\omega t-\vec k\cdot\vec r)}$$
and with it's corresponding $E$ field. This is ...
0
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0answers
41 views
EigenMode expansion for beam propagation
I want to understand how to apply EigenMode expansion method (http://www.photond.com/files/docs/PW03_eme_paper.pdf) for beam propagation on a system of lenses.
The interface between two mediums of ...
0
votes
1answer
67 views
Is there a formula for determining the focal point of a sphere?
I guess this is the same as for cylinders, when light is shone through parallel to the cross-section, but Google-ing this only turns up lenses like the ones used in glasses.
I'm looking for something ...
2
votes
1answer
180 views
Different colors in LED/LCD display when viewed from different angle?
I want to know why different colours appear when viewed with a different angle. Can anyone tell me why?
5
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1answer
2k views
Newton's color Disk
How does Newton's color disk work?
Newton's disk - Take a circular white color disk, make 7 equal intersections and paint section with respective VIBGYOR colors, now when you spin the disk in certain ...
15
votes
3answers
31k views
Virtual vs Real image
I'm doing magnification and lens in class currently, and I really don't get why virtual and real images are called what they are.
A virtual image occurs the object is less than the focal length of ...
4
votes
0answers
80 views
How can some optical microscopes measure height differences of different sample planes with nanometer accuracy?
I could use last week an optical microscope, didn't seem special in any way, 50x magnification, image viewable per a CCD camera on a computer screen besides through the ocular.
But the software of ...
5
votes
2answers
134 views
What is the minimum optical power detectable by human eye?
If one is in complete darkness, what is the minimum optical power that the eye can "see" (let's say in 500-600 nm range).
I found that for 510 nm, 90 photons can be detected ...
2
votes
1answer
49 views
Where did this equation come from ∠I+ ∠E = ∠A+ ∠D?
∠I+ ∠E= ∠A + ∠D
Angle of incidence + angle of emergence = angle of prism (Normally 60°) + angle of deviation.
If their sum is not equal,we made personal error in doing an experiment with prism. ...
2
votes
1answer
79 views
Photon in a weighted superposition of states
Consider an experiment that produces photons in an entangled state such as $1/\sqrt{2}(|{H,H}\rangle+|{V,V}\rangle)$. The photons are in a superposition of horizontal and vertical polarization, and ...
6
votes
3answers
2k views
How does a photon travel through glass?
This was discussed in an answer to a related question but I think that it deserves a separate and, hopefully, more clear answer.
Consider a single photon ($\lambda$=532 nm) traveling through a plate ...
1
vote
2answers
74 views
All mirrors always shrink to 50% scale?
I have this geometric optics exercise here, in which a man is looking at himself in a mirror.
Determine the minimum height at which the bottom of the mirror must be placed so the man can see his ...
2
votes
1answer
289 views
What's the mathematical background to the representation for Gaussian beams?
Background
A general optical system (not necessarily having an axis of
rotational symmetry) can be represented, for small deviations from a base ray,
by the matrix transfer equation,
$$
...
1
vote
2answers
163 views
Why does light not refract when incidented perpendicularly?
I had read that light does slow down in glass because photons interact with atoms in glass. They are absorbed and re-emitted and during this phenomenon it's speed decreases. See also this and this ...
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0answers
40 views
Weakly Guiding Approximation
I was reading a chapter on Fiber Optics and I encountered Weakly Guiding Approximation. I am reading John M. Senior and it says ...
3
votes
2answers
188 views
What is a two-photon process?
I am reading some introductory materials on modern optics, in which they mention two-photon processes everywhere. I know fundamental optics and a bit on quantum mechanics. Can anyone explain in a ...
40
votes
3answers
1k views
What causes insects to cast large shadows from where their feet are?
I recently stumbled upon this interesting image of a wasp, floating on water:
Assuming this isn't photoshopped, I have a couple of questions:
Why do you see its image like that (what's the ...
1
vote
3answers
381 views
Why does change in speed of a wave make it refract?
When a light wave enters a medium with a higher refractive index (e.g. from air to standard glass) and its speed decreases, why does that make it refract/bend?
I understand that wavelength decreases ...
0
votes
1answer
98 views
Correcting for bad eyesight on display monitors [duplicate]
I think it would be neat if one could configure one's eyesight parameters (astigmatism and myopia in my case), viewing distance, and perhaps age into a special display driver, such that a computer ...
9
votes
7answers
3k views
Why is a 1mW laser dangerous?
In our Physics lab we have a 1 milliwatt (0.001W) helium neon laser. Despite the low power, we were cautioned not to even look at reflections of the beam as it could cause permanent eye damage - why ...
0
votes
1answer
163 views
calculating focal length of meniscus lens
As I read about telescope, distance between objective lens and eyepiece must be equal to addition of their focal lengths.
D = F1 + F2
I used one of the eyepiece ...
1
vote
1answer
84 views
Eikonal approximation for wave optics. Why follow the unit vector parallel to the Pointing vector?
The description of the passage from wave optics to geometrical optics claims that light rays are the integral curves of a certain vector field (the Pointing vector direction, normalized to 1). Here ...
2
votes
1answer
133 views
What is the cause of orange sky glow?
I live in the Netherlands and recently I have been seeing an orange glow in the sky at night, in the northwestern direction. What is the cause of this? And why is it in the northwestern direction (I ...
6
votes
2answers
277 views
Where does energy go in destructive interference? [duplicate]
I have read that when two light waves interfere destructively, the energy contained within is transferred to other parts of the wave which have interfered constructively. However, I am having some ...
1
vote
1answer
43 views
Why is spectral sensivity of a photodiode expressed in A/W
Can someone explain me the meaning of the A/W unit of the photosensivity when reading a spectral response function of the wavelength characteristic of a photodiode?
2
votes
2answers
57 views
Optical trapping problem
Can we make light slower by applying optical trapping (I mean applying laser beam to lower the speed of light)?
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vote
0answers
11 views
Speed of Light in a Medium [duplicate]
For light travelling in a medium with refractive index greater than one:
The "average" speed of light is slower than the speed of light in a vacuum. As far as I know, the instantaneous speed of light ...
0
votes
1answer
41 views
Optical refocusing efficiency
What is the material for optical focusing that produces the less diffraction losses?
Suppose one have a sequence of serial optical elements $R$ that keep refocusing a beam of collimated light, each a ...
2
votes
1answer
82 views
Factors that make beam divergence worse after refocusing
A beam of light of width $W$ and wavelength $\lambda$ with divergence that is diffraction-limited is refocused with an optical element placed at a distance $D$ from the beam source. Will the refocused ...
5
votes
3answers
872 views
Why don't waves with different wavelengths interfere with each other in white-light?
The book I'm reading about optics says at some point that "each color (wavelength) contained in the white light interferes only with itself". But why is this so?
Edit: I moved the rest of the ...
3
votes
2answers
296 views
How to make the projected image smaller by adding one ore more lenses in front of the built in projector lense?
I have a projector that creates a large image, even if the distance to the screen is short. The device is very small, approximateley 10x10 cm if you look from above. The height is only 3 cm.
I ...
3
votes
2answers
165 views
Redirecting light beams from beam splitters
I'm doing a project where I am taking a laser beam and sending it through a beam splitter. As I understand, approximately 50% of the light will go pass through and 50% will be reflected. So this means ...
1
vote
1answer
155 views
Thin lens formulae
Hi I have a question about applying the thin lens formula
$$ \frac{n_1}{s_o} + \frac{n_2}{s_i} = \frac{n_2 - n_1}{R} \,\text{thin lens formula}$$
for a single lens emerged in medium $n_2$ in the ...
3
votes
1answer
149 views
Computer-Generated Holograms: I'm completely lost. How are they physically implemented?
I have been reading about holography, and I think I understand the general concept, but one thing that has me completely lost is how computer generated holography works in practice.
I think I get the ...
34
votes
1answer
3k views
Why does a window become a mirror at night?
In day, when you look in the room through the window out, you can clearly see what happens outside. At night when it's dark outside but there's light inside you can look in the window but it becomes a ...
14
votes
2answers
392 views
Can't seem to reconcile geometric optics and wave optics
I was looking at a physics situation involving light, and I can make the correct derivation assuming light is a ray of a given intensity (geometric optics), energy conservation checks out, everything. ...
3
votes
2answers
273 views
Hartmann mask based collimation
Is there a detailed description for a Hartmann mask based collimation process?
I've been told by a friend that is possible to collimate an SCT by placing a three round holes Hartmann mask at the ...
3
votes
3answers
44 views
Quality loss when adding more components to a telescope?
I would think this would be inherently true, but I'm curious:
(Assuming the highest quality amateur instruments are used.)
Is quality lost when, say, adding a T-mount adapter, diagonal or any other ...
