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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images of objects at infinity

Is the focal point of our eye lens is on the retina? if it is so why dont we see point image of infinite object because light rays coming from them are parallel to each other and converges at focal ...
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0answers
24 views

3D glasses and reflection/polarisation [duplicate]

Hi all, Tonight I'm going to see a 3D film so I thought I'd check whether I had any old 3D glasses around the house. Found a pair of "RealD" glasses. Anyhow, I assume that the glasses use some ...
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1answer
32 views

Gaussian beam shape

In this diagram of a Gaussian beam, why does the radius vary with z position? Is it assumed that a Gaussian beam is always being focus by a lense? Why can the beam not go any smaller than $w_0$ and ...
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1answer
53 views

A Difficulty with Liquid Metal Mirror Telescopes

"Another difficulty is that a liquid metal mirror can only be used in zenith telescopes" [Wiki] Why is that? Why can't a series of flat mirrors be used to reflect light coming from any angle to be ...
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1answer
28 views

Asymmetric photoluminescence spectra

Why do photoluminescence spectra have asymmetric lineshapes as those here http://www.scielo.br/img/revistas/bjp/v37n4/a04fig01.gif or here: ...
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0answers
28 views

Rayleigh Criterion and Resolvability

If I want to resolve two close but different wavelengths $\lambda_{1}$ and $\lambda_{2}$ to the second order in my experiment using a grating of spacing $d$, is the size of the grating ($D = Nd$) I ...
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62 views

How can I precisely measure the intensity of the Hydrogen Alpha (Balmer) line at low intensities?

I assume that I will need some kind of very precise filtering, but how is that accomplished? After that, photon counting at worst, but I am expecting millions of photons per second. The background is ...
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1answer
40 views

Sampling a 2-dimensional surface: How many samples along X & Y axes?

I have a set of first 25 Zernike polynomials. Below are shown few in Cartesin co-ordinate system. z2 = 2*x z3 = 2*y z4 = sqrt(3)*(2*x^2+2*y^2-1) : : ...
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2answers
74 views

Momentum change of a photon upon diffraction at a grating

How is the momentum change of a photon is related to the grating periodicity and diffraction order? I came across with this question while studying surface plasmon polaritons (SPPs) and how to excite ...
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1answer
55 views

Power of several focused laser beams on a small surface

After viewing this: My Homemade 40W Laser Shotgun Will the initial 40W power of the diodes beams be roughly transferred to the targeted surface where the 8 beams are focused, or will there be a power ...
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0answers
22 views

Why did the reflection coefficient of quarter-wavelength coating depends on the indices of refraction

It was derived in page 428 of Optics by Eugene Hecht (4ed), that in the configuration below: where $$d = \lambda_f / 4 $$ The reflection coefficient R is So when $n_0n_s=n_1^2$, the reflection ...
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2answers
73 views

Shimmering from heated air and the speed of light

A few months back, I was using binoculars to check if my friend was on his boat, which was around 2 to 3 km out to sea from the shoreline where I was standing. The images from, say the sail of the ...
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0answers
19 views

Spherical Aberration Of Electron Lenses

I would like to know why electron lenses can't have negative spherical aberration. Every textbook I have found devotes one or two sentences to saying that Otto Scherzer prooved this 80 years ago, but ...
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1answer
26 views

What wavelength of light is the term 'focal length' defined against? [closed]

Because different wavelengths of light are bent differently in a medium, the focal length ought to be different for each of them (which is why white light splits up into a rainbow). If I have a "25 mm ...
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0answers
20 views

What are the physical optical limitations photonic metamaterials can offer?

Modern technology has introduced new photonic metamaterials that can extend optical properties beyond what standard materials can offer. For example a negative index of refraction is now possible ...
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1answer
65 views

If I wear contact lens and spectacles of same power, is it same wearing thick spectacles of twice the lens power?

Assume I have a contact lens of power -1 and a spectacles of +1. Will they cancel out their effect? is it same as my normal eye sight?
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4answers
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Explanation of Michelson Interferometer Fringe Shift

I have been working on an experiment where 2 glass microscope slides are pinched together at one end (so that there is a "wedge" of air between them) and placed in the path of a laser in one leg of a ...
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1answer
61 views

does photon travels in a helical path in an optical vortex?

The wave front of the optical vortex beam is helical. Does it mean that the photon travels in a helical path? When the optical vortex beam is focused on a screen, an annular ring with dark center is ...
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1answer
39 views

Conditions for having refractive index less than unity?

Is it possible to have an index of refraction, $n < 1$, giving the "illusion" of a speed greater than $c$. As far as I understand it, is only the phase-velocity (which does not carry any ...
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0answers
57 views

How to properly implement Huygen's integral?

I'm really confused by what's happening ... I'm trying to propagate a beam some distance and compare initial and final intensities. Lets say the initial electric field is just cos(200x). I then used ...
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1answer
31 views

Is this picture sign of diffraction? [duplicate]

Please tell me that can it be the sign of diffraction? I mean can diffracted rays make this pattern?
6
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1answer
84 views

How deep is a rainbow?

My cousin shot this photo of a rainbow in front of a mountain. In the picture it is clear that the mountain is behind the rainbow (the rainbow blocks the view of the mountain), whereas the nearby ...
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1answer
44 views

Would the Hubble Space Telescope be of benefit for optical astronomy at Lagrangian L5 point?

The Hubble Space Telescope will enter a decaying orbit in 2024. This is a physics based question, so I don't want to get into the engineering details more than necessary. Just for background, the ...
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1answer
19 views

Use two polarizing filter without liquid crystal between them to render static image

I'm going to demonstrate the work of polarizing filter. I have a tablet for this purpose with disassembled LCD panel which is fine but it is bulky and overkill. Is there any other material that may ...
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0answers
24 views

Is local oscillator light polarised?

If a laser is used as a local oscillator in the homodyne setup does this mean the light it produces is polarised? (I am looking at this from the context of quantum physics and random number ...
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1answer
30 views

Patterns in a spinning wheel [duplicate]

Why do we see patterns on a rotating wheel with spokes which seem to rotate counterclockwise or clockwise as and when the wheel accelerates or deaccelarates. What I mean is the patterns like this
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1answer
42 views

Textbooks or papers that clearly explain second harmonic generation?

I'm having trouble learning about Second Harmonic Generation. I've found a bunch of sources, but they all seem to expect a fairly advanced level of knowledge about it. For example, in the wiki section ...
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How to recover an unfocussed image

If the lenses in a camera are not set correctly, the intended subject will be "out of focus" in the resulting image. There seems to be no loss of information here. The photons are just steered to the ...
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0answers
11 views

Regenerative Amplifier

I want to ask the questions dedicated Optics (or Laser Physics). What is the difference between laser amplifier and laser regenerative amplifier? What is the average pulse duration of Nd:YAG laser ...
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1answer
48 views

Michelson-Morley experiment

I have to do an experiment about light. I preferred to measure the speed of light by the experiment of Michelson and Morley. When you do the experiment, it will result in an interference pattern by ...
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0answers
30 views

Chromatic aberration in human eye [duplicate]

A lens focuses the different colours of white light at different points. Since our eye has a convex lens there should also be such an aberration but we see objects clearly with normal eye. I want to ...
4
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5answers
212 views

What about a surface determines its color?

Light falls on a surface. Some wavelengths get absorbed. The other are reflected. The reflected ones are the colors that we perceive to be of the surface. What is the property that determines, what ...
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1answer
51 views

Why do we use Mie scattering to describe light scattering off large objects?

I'm an undergraduate student who has recently come across Rayleigh and Mie scattering and I'm trying to understand them a little better. As I understand it Rayligh scattering is used only when the ...
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1answer
66 views

Combination of two concave lenses

When we have two convex lenses in contact we have the combination behaving as a converging lens. Can someone please give an analytical description for the combination of two concave lenses in contact ...
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23 views

statistical property of light reflected from a coarse mirror

This is a problem comes up in my study in correlation reflectometry. I'm wondering if there is a straight-forward way to interpret the phase and amplitude of the reflected light from a perturbed ...
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26 views

Magnification: Microscopes Telescopes

What is the difference between the way a microscope magnifies say a star and a telescope say a cell? Why is it, that the eyepiece of a telescope magnifies stronger when it is smaller and with a ...
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0answers
32 views

Derive phase shift equation for two diffirent optical paths differences

If we have two optical paths differences, call them $\phi_1, \phi_2$, and $\phi_1 > \phi_2$ then phase shift with respect to optical path difference $\phi_2$ is $PhSh = \frac{2\pi}{\lambda}(\phi_1 ...
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0answers
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Limits on the information obtained through optical measurements

Consider a Gedankenexperiment shown in the figure below. There are two lasers $S1$ and $S2$ with exactly the same specifications on paper. In practice, they are of course somewhat different but ...
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images formed by refraction

While deriving the formula for image formation by spherical refractive surface we assumed that object is placed at the principal axis and is like a point object. What if the object is not placed at ...
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0answers
21 views

image motion for projectile motion of object

a ball is projected from top of the table with initial speed u at an angle of inclination 'a' to the table. describe motion of image with respect to the ball on a screen located next to the table My ...
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0answers
31 views

Plane wave conditions

Which conditions have to be fulfilled in order to approximate a light beam by a plane wave (i.e. $\phi(x)\approx \phi(0)e^{ikx}$)? I am looking for both mathematical and experimental conditions. At ...
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1answer
52 views

Reflectivity of Metals - real and imaginary part of k-vector and complex dielectric function

De electric field component of an electromagnetic wave that is traveling in the $x$-direction is given as $$E(x,t) = E_0 e^{i(kx - \omega t)} $$ with $E_0$ the amplitude and $k$ the wave vector. From ...
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1answer
38 views

Optical path difference

Hello, i have question about calculating optical path difference. $\Delta L = (BC+CD)*n2 - BF*n1$ - why calculating path difference here we are substracting $BF$ segment?
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1answer
43 views

Oberving a photon through double slits

If we send a particle with mass through the double slits we observe a interference pattern. That is of course if we don't observe which slit the particle goes through. If we do then we get two peaks ...
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3answers
108 views

Violation of conservation of energy?

Imagine a perfectly spherical mirror with 100% reflection. Imagine a point source of light in the center. The point source keeps radiating light. Will the light undergo destructive interference ...
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0answers
23 views

Any good reference on crystal optics?

I am primarily interested in the birefringence phenomenon. Any good reference? I want something above the general physics level.
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9 views

How does voltage sensitive dyes actually determine neural network in foetus?

In research topics of neurophotonics, the best way of determination of neural network in foetus is by using voltage-sensitive dyes instead of placing diodes. But how does it actually work? Sorry if ...
1
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1answer
39 views

Can someone give an intuitive understanding of Fano Resonance?

I'm reading about Fano Resonance. The line that almost every source I can find gives is something like (from the wiki): The Fano resonance line-shape is due to interference between two ...
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2answers
47 views

Measuring image distance of a virtual image

How to a measure image distance of a virtual image without calculation? It is impossible? To measure it, we must have a real image to measure the image distance with a screen and a ruler. I saw it ...
5
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1answer
62 views

Long, blurry reflections in wet road [duplicate]

When driving on a wet highway at night, any surface emitting or reflecting light will have a reflection right under it that is blurry and seems to stretch to infinity. This is not exactly what I am ...