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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How do you calculate heat flux (Kw/m2) at the focal point of a mirror? [duplicate]
can anyone help me to determine the heat flux (Kw/m2) on a focal point of a parabolic dish having a diameter of 1.5 meter and a focal length 60 cm ???
please awaiting your soonest reply for my senior ...
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2answers
97 views
Why don't you see multiple images of an object?
Consider the ray model of light. Let's say an object such as a pencil is illuminated, and consider one point on that pencil. Since there could be many rays of light bouncing off the same point on the ...
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4answers
143 views
Effects of surface roughness on specularity
Say you have a piece of glass, which looks specular if propery cut/polished. But if you sand the surface using say sand paper, it will look hazy and glossy. I'm wondering how much surface roughness ...
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1answer
244 views
Why does the sky look black in pictures taken from the summit of everest?
In pictures taken from the summit of Mount Everest (such as this one), the colour of the sky is a very dark blue or even black in some pictures. I remember from my own experiences of hiking in the ...
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1answer
55 views
Fraunhofer diffraction simulation for a hexagonal aperture, what are the typical units?
Kostya answered a question that was asking what the diffraction pattern looks like for a hexagonal aperture in front of a lens. He lists an equation which was derived using a Heaviside function to ...
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2answers
135 views
Why does the index of refraction change the direction of light
I've been studying in optics the macroscopic maxwell's equations, and how electromagnetic fields propagate through different mediums. Over there, the index of refraction appears, as a complex function ...
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1answer
63 views
Which fraction of light is refracted from a source of light under a lake?
I was trying to solve this problem:
"A punctiform source of light is standing inside a lake, at a height h of the surface. f is the fraction of the total of energy emitted that escapes directly from ...
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1answer
50 views
double slit experiment with two opposite quarter waveplates
Consider the usual double slit experiment involving laser and a double slit and a screen. Now place in front of the left slit a quarter waveplate (let's call it QWP1) that changes a certain linear ...
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163 views
Why a person with a further near point experience a larger magnification with a magnifier
Two people, Micah and Lyra, with different near points are equally
close to an object. Both inspect the object through the same magnifier
by holding the lens close to the eye. Micah's near ...
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1answer
68 views
What determines the sign of an image distance?
A lens placed at the origin with its axis pointing along the x axis
produces a real inverted image at $x = - 24 cm$ that is twice as tall as the
object.
What is the image distance?
Why ...
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2answers
189 views
How do you calculate power at the focal point of a mirror?
I'm a Mechanical Engineering student and I'm working on my senior project, so I need help. My project is about designing a solar dish having a diameter of 1.5 meters and a focal length of 60cm. so at ...
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1answer
140 views
Polarizability and the Clausius-Mossotti Relation
There seems to be a fairly large inconsistency in various textbooks (and some assorted papers that I went through) about how to define the Clausius-Mossotti relationship (also called the ...
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51 views
cgs Gauss' system of units
I had never seen this system until today, and I'm really confused. I've read the wikipedia article about it but I still don't know how to change between this and the international system. For example, ...
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4answers
228 views
Eye sensitivity & Danger signal
Why are danger signal in red, when the eye is most sensitive to yellow-green?
You can check luminosity function for more details...
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1answer
141 views
Is a holographic recorder able to capture a large full color picture? [closed]
Is it practical to attempt to build a 3D hologram generator that is full color and big enough to recreate a watermelon full size? If so, is real-time control feasible?
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59 views
Are EM waves scattered the most when the wavelength and the obstacle have a similar size?
I heard that when the wavelength and obstacle are similar in size, the scattering is the greatest. Is this true?
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1answer
79 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 ...
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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 ...
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2answers
67 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 ...
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70 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?
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3answers
38 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?
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0answers
107 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 ...
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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 ...
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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 ...
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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 ...
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2answers
89 views
Gravitational distortion of an object's diameter, at a distance,
Does the curvature of space-time cause objects to look smaller than they really are? What is the relationship between the optical distortion and the mass of the objects?
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1answer
66 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 ...
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1answer
74 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, ...
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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. ...
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1answer
76 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 ...
5
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2answers
132 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 ...
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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 ...
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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 ...
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1answer
142 views
Maximum theoretical bandwidth of fibre-optics
Ignoring hardware at either end and their technological limitations, what is the maximum theoretical bandwidth of fibre optic cables currently in use / being deployed in a FTTH type situations? I ...
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2answers
156 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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1answer
92 views
Liouville's theorem and gravitationally deflected lightpaths
It is customary in gravitational lensing problems, to project both the background source and the deflecting mass (e.g. a background quasar, and a foreground galaxy acting as a lens) in a plane.
Then, ...
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1answer
119 views
What is the effect of refractive index of an object for imaging?
My Question is as follows.
What is the effect of refractive index of an object for imaging (Photographs by high speed camera) on its size and shape information incurred from image?
Lets say ,
I ...
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39 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 ...
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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 ...
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2answers
111 views
How to calculate the height and length of a reflected ray?
I barely know anything about optics, so I could use some help about how to go about solving this problem.
If I have a ray of light at a certain height from the optical axis, propagating at an angle, ...
5
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3answers
216 views
Why is visible light used in Optical fibers (instead of other EM waves)?
Why aren't other electromagnetic waves used in optical fibres instead of visible light?
Is it because the wavelength of light fits the internal reflection/refractive index of the material used for the ...
6
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2answers
266 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 ...
3
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2answers
184 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 ...
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1answer
80 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 ...
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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?
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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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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 ...
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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 ...
2
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1answer
78 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 ...
