# Tagged Questions

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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### Why don't windows and mirrors cancel light?

So I understand that when light goes from a material of low index to a material of higher index it picks up a phase change of 180. Most glass has an index of around 1.5. I know that when light goes ...
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### Analytical calculation for focus deviation

How can I analytically calculate the deviation in focus or focal length variation in a situation as shown in figure. When the Sensor is parallel to the face of the lens/ light; its easy to calculate. ...
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### How was microscope-level zoom created by a lens and a water droplet?

It was a rainy night. My glasses were speckled with fresh water droplets. I looked at a distant street light and I was surprised to see cells - a single cell was zoomed in to the level where I could ...
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### Geometrical Optics- spherical surface [on hold]

A spherical surface of roc 10 cm separates 2 media x and y of refractive indices 3/2 and 4/3 respectively. Centre of the spherical surface lies in the denser medium. An object is placed i x medium. ...
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### Difference between linear magnification, axial magnification and aerial magnification (w.r.t. mirrors)? [on hold]

Please explain how the three types are different from each other using pictures (preferably) or diagrams. And if possible, an explanation regarding how each would be different for mirrors and lenses ...
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### Why do thin films need to be thin?

No matter what thickness a piece of glass is wouldn't its optical thickness be close to an integer multiple of a wavelength such that it could create interference effects? I feel like I am missing ...
So I am imagining a piece of glass with an index of $n = 1.5$ Lets say that a beam of light is coming in from air $n=1$ at normal incidence. I was using the equation for the reflection coefficient: ... 3answers 58 views ### How to distinguish light rays coming from objects of different material Motivation: My major focus is on Digital Image Processing (specifically segmentation). Due to external noise, the different parts of an image are not fully quantized. Therefore, various segmentation ... 1answer 81 views ### Physics of detection of coherent light in an incoherent background using the more compact Fabry Perot interfeometer? I read University Of California Berkeley Professor J. Bokor's Chapter 7 course notes , shown below as an imgur image , on Temporal Coherence tonight. I am sending an email to Professor J. Bokor ... 2answers 78 views ### Why is it easier to get sunburnt in the water? [duplicate] I went today to the swimming pool and I remembered that when I was younger my mom used to tell me to be careful because you get sunburnt much more easily in the water than in the ground. I never gave ... 0answers 34 views ### How to solve this problem? [on hold] A convex lens of focal length 16cm forms a real image of double the size of object. What will be the distance of object from the lens? 3answers 55 views ### Is the light emitted by a laser a 'beam' or a 'ray'? [on hold] In English, the light generated by a laser is almost always referred to in technical texts as a 'laser beam'. However, in French, Spanish, Portuguese and Italian, forms that correspond to laser beam ... 1answer 31 views ### Center of gravity of the photon beam I have a conceptual question: In singular optics the orbital angular momentum (OAM) is represented by two components: intrinsic (no relation to spin!) and extrinsic. The first one is associated to ... 1answer 34 views ### How are iris diaphragms used in laser alignment? I've read in many places that one of the canonical uses of iris diaphragms is to align a laser beam, but I'm having trouble understanding how this works, since I can always setup a set of arbitrarily ... 1answer 17 views ### fiber optic face plate physics-opaque to transparent behavior based on distance of object? Please look at this video below. its of fiber optic plate or compressed fiber lens Here it seems that the object- which is the book or letters here, is visible only when the plate is touching the ... 0answers 23 views ### What is the purpose of condenser lenses in the slide projector shown below? [duplicate] I searched a lot on internet about this.I could not find the working of these condenser lenses in detail. Some websites say that condenser lenses make the light rays parallel and to pass through ... 3answers 61 views ### what is the purpose of condenser lens in a slide projector? What if we don't use any condenser lens? can't we use a single convex lens as a condenser? what difference will it make? kindly explain it in detail. 1answer 28 views ### Why anti-reflective coating of silicon nitride colour varies with thickness? Why the silicon nitride colour varies with the thickness? 1answer 37 views ### Reflection and refraction of single photon incident on a glass slab If a single photon strikes a glass slab of certain thickness, can we make prediction whether it would reflect or refract? On which factor the reflection or refraction of single photon through such a ... 0answers 13 views ### opaque to transparent based on distance of object? If we look through a transparent glass window of an apartment, from a distance in day light, we can’t see what or who is inside. All the light is reflected off the surface of the transparent glass ... 2answers 79 views ### Why do we restrict to electric field when describing light? Why do we restrict only to electric field when describing light as electromagnetic wave? I mean from Maxwell equations we can derive wave equation for electric field and also for magnetic field but ... 1answer 22 views ### What makes an object reflect the colour that we see? If a rubber ball is red, I know that it is absorbing all colours except for red, which it is reflecting. So there is not actually a part of the object that contains any red. But what tells an object ... 0answers 15 views ### How to converge two independent point light sources with a single biconvex lens (20D) I need to take an image of fundus of an eye. So I'm using a 20D lens to see the fundus. Camera is kept in the same axis and eye is illuminated by two 3v LED's. The LED's are placed just at the edges ... 0answers 19 views ### What characteristics of incident light changes upon reflection I am searching for various characteristics of incident light that get modified or changed in reflected light compared to incident light. Light could be monochrome or multi-chrome. I am looking into ... 1answer 43 views ### How come we can get mirror-like effects from dark surfaces? Question: If I understand correctly, an object's color is determined by the optical frequency which it does not absorb. So an apple appears red because it only reflects red. My question is, if this is ... 0answers 32 views ### Cheap DIY Zernike-Phasecontrast: Optical Thickness of a inkjet/laser printed contour for phasering? [closed] Rough guess: Optical Thickness of a inkjet/laser printed contour? Edit I was wondering if there is any research regarding the refractive index and the height of an inkjet or laser printed contour? ... 1answer 22 views ### Reason for absorbance First quoting the example which raised my curiosity"when light passes through polaroid it absorbs certain direction light rays" My question is how this phenomenon of absorbance occurs is this some ... 0answers 34 views ### optical properties of metal-dielectric-metal microcavities I would like to figure out the optical properties of metal-dielectric-metal microcavities, used in the fabrication of micro patch antenna. The paper that I'm reading is this one. Now the specific ... 1answer 30 views ### Does crossing your eyes to see stereoscopic images provide the same effect as unfocusing your eyes (looking into the distance)? Not sure if this is the best place to post this. Please correct any formatting/grammatical errors I've made! 0answers 33 views ### How small can a spherical clear glass bead be before it loses it's transparency? I don't know if it'll help but I'm trying to use these as tracker particles in water. Edit: I mean it'll start scattering light. I know glass beads of size about 30 micron and less appear white under ... 2answers 80 views ### Does every past state of the Earth currently “travel” through the universe? So I just read this question. The 27 year old user asks if it would be possible to see his own birth if he would be 27 lightyears away from the earth and the answer states ... 0answers 34 views ### Does the curvature of the IMAX screen improve the view of 3D video projections in any way for viewers not sitting in the “sweet spot”? When I think about a simple 2D projection on a screen with vertical-cylinder curvature and of viewing positions away from the "sweet spot" it seems to me pretty obvious that there would be geometrical ... 0answers 23 views ### Double Fraunhofer , Fourier transform to the image plane? Consider the diagram below: I know that from Franhofer diffraction we have: $$u_f(x_f)\propto \int u_o(x_o) e^{-k\frac{x_f}{f}x_o} dx_o$$ Assuming small angles. I also know thatu_i(x_i)$is ... 0answers 44 views ### What is abbe's rule in optics? I have read wikipedia but can't really understand what they mean to say. The usual explanations are given in terms of Fourier optics, which I don't yet have the background for. Can anyone explain it ... 1answer 53 views ### What are these microscope circles? This is a photo I have taken with a microscope (100x objective). What are these circles? When I rotate the eyepiece or the objective they stay still. Are they particles on the mirror? In this case ... 0answers 34 views ### Large angle of incidence equation for the Fabry Perot interferometer What is the large angle of incidence equation for the Fabry Perot interferometer operating in the visible light spectrum? Most optics textbooks only derive the small angle of incidence equation for ... 0answers 29 views ### What is the angular dispersion of an optical surface grating and why does the textbook answer seem to violate reciprocity? The behavior of a surface grating can be described by the grating equation$m\lambda=d(\textrm{sin }\theta_i+\textrm{sin }\theta_d)$[1] with$m$: diffraction order,$\lambda$: wavelength of the ... 0answers 66 views ### Time involved in reflection Consider light bouncing back and forth between two ideal front surfaced mirrors. How long does the process of reflection (i.e., absorption and re-emission) take? 1answer 39 views ### Proving that angle of incidence over angle of reflection is constant in Snell's Law First let me state what I think I know: Snell's Law states that$\frac{sin(i)}{sin(r)} = \frac{v_1}{v_2}= \frac{\lambda_1}{\lambda_2}= \frac{n_2}{n_1}$where i is the angle of incidense and r is the ... 1answer 123 views ### Quarter-wave stacks and rejection filters to protect flight crews' vision from visible laser pointers [closed] I would like to know how the physics(and possibly mathematics) for how quarter-wave stacks could be utilized to make an ideal rejection filter that rejects all visible coherent green or blue or red ... 1answer 37 views ### On parabolic concave mirror in car flashlights Sorry for the seemingly silly question but what's the advantage of having a concave mirror in car flashlight? I understand how the physics works but I just don't get what the advantage of having this ... 0answers 18 views ### Hologram: How does the interference path of reflected and reference waves change as we move? I've seen this and this and read this. Either I got dumber in times or these are not sufficient to understand how actually hologram works. I understand how reference light and reflected light ... 0answers 56 views ### Why is 2000 grit good enough for a mirror finish? The mean particles size on a 2000 grit sandpaper is ~ 1 um, which is not that smooth compared with the wavelength of visible light. But usually when I want a mirror finish, 2000 grit will provide a ... 1answer 22 views ### Do the intensities of the light sources affect the Rayleigh Criterion of minimum optical resolution? I'm currently a physics student studying the optics unit. I learned that the Rayleigh Criterion is usually used to define minimum optical resolution. The equation for the criterion is θ=1.22 λ/d where ... 0answers 17 views ### Fiber Optics - Mechanically Induced Long Period Fiber Grating I created a grooved plate with a groove spacing of 650 microns which I used in an experiment to produce a mechanically induced LPFG(Long Period Fiber Grating). I measured the transmission spectrum ... 1answer 46 views ### Birefringent filter, optical path length difference? In 'The Light Fantastic' by Kenyon, I.R. (p424), it is said that for a birefringent material inclined at Brewster's angle and who's optical axis lies in the plane of the plate, we have an optical path ... 0answers 17 views ### Broad Spectrum Contact Lenses - How Soon? Given the amazing advances in metamaterials, how soon will we have the means to view a broad spectrum of electromagnetic radiation (IR through UV) by having it faithfully compressed into the range of ... 1answer 40 views ### Fourier optics (diffraction from pinholes) A plane wave of wavelength$\lambda$and unit amplitude is normally incident on a mask placed in the xy-plane at$z=0$. The mask contains two infinitesimally small pinholes, located on the x-axis ($y=...
I am working on a very phase sensitive planar dielectric waveguide device and I need to calculate the phase delay induced by a bend of some radius, $r$ and of $\phi$ radians for a give planar ...