What is Optical: Definition and 696 Discussions

Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.Most optical phenomena can be accounted for by using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.
Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics. When considering light's particle-like properties, the light is modelled as a collection of particles called "photons". Quantum optics deals with the application of quantum mechanics to optical systems.
Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fibre optics.

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  1. T

    Spin orientation by optical technique

    Could you teach me about spin orientation by optical technique. Thanks a lot!
  2. xunxine

    Can You Bend Optical Fibres Too Much?

    Although optical fibres do not break easily, is it possible to bend the optical fibre too much that light that travels within the optical fibre will strike the wall at less than the critical angle and thus escape from the fibre through the wall? Pls enlighten me. Thanks! (I came across this...
  3. G

    Help needed: coupling light from a LED into an optical fiber

    First let me preface this by saying by physics-fu is remedial at best. I am a neuroscientist by training, but need a little help with piece of equipment I am designing, so any ideas or input would be greatly appreciated. Basically, I need to figure out a way to efficiently couple a light...
  4. S

    Pyro Optical Pyrometer by The Pyrometer Instrument Co. - Model/Type?

    A friend has just given me a beautiful 1960-ish optical pyrometer. It is a Pyro Optical Pyrometer, made by The Pyrometer Instrument Co. with serial number 14081. Cannot find model or type. Now. To the questions. Does anyone know how this thing works? The physics I understand slightly, as...
  5. J

    What's the recoil energy in optical lattice?

    Will anyone give me an explanation helping me understanding it?
  6. P

    Laser optical components/setup

    Hi I just started a PhD where I am going to use lasers to measure fluid flow among other things. I am looking for some helpful information about otpical components and techniques mainly relating to lasers. How to correctly design a setup, how to split beams, how to expand/contract beam...
  7. H

    Optical Solitons - General understanding and Project ideas

    Homework Statement I have written a working program that can obtain a numerical solution to the nonlinear Schrodinger equation, given at initial pulse, using the split-step Fourier method. I have performed the first task of writing a working programme and have shown that if the initial...
  8. L

    Optical Microscope Homework: Calculating Magnification & Viewing Distance

    Homework Statement Hi. I'm required to calculate the magnification of a microscope with the variables given. I have calculated this, but was just wondering if the best viewing distance is bigger than the length of the microscope, would this have any effect? Homework Equations N/A The Attempt...
  9. X

    What is the hidden image in this optical illusion painting?

    It looks like a leopard, and it is a painting, but there's more to it... Anyone see it? :biggrin: Hint:
  10. J

    Help with Images and Optical Instrument Question

    An object is placed two focal lengths from a diverging lens, (a) What kind of image forms? (b) What is the magnification? (c) Where is the image? I am pretty sure the image is virtual, as for (b) and (c) I have no idea what to do.. Looking for some help, thanks in advance.. (a) I am...
  11. T

    Optical Diffraction: Double Slit & Gratings

    Homework Statement first question; Does a double slit also diffract light of different wavelength into different directions? second question; How would a diffraction grating for cm waves differ from an optical grating? Homework Equations sin (theta) = m.Lambda / d maybe, i am unsure...
  12. P

    Optical band-pass filters (radome coatings)

    Hi, I am reading about a new field that I am not familiar with at all, and I was hoping that someone could give me some info on that. The general idea is that if you have a conductive layer, with a periodic array of apertures perforated in it (such as crosses), you can design a band-pass...
  13. S

    Calculating optical power output

    Homework Statement A blue semicon LED is connected in series with a 10ohm series resistor to a voltage source. The LED emits 4.03 x 10^16 photons/s at a wavelength of 400nm. The current flowing through the LED is 40mA and the voltage across the LED is 3.5V. Calculate the power conversion...
  14. thenewmans

    Space.com says intergalactic hydrogen gas absorbs all optical light

    What? Is there any truth to this? The caption on a space.com photo of the oldest object ever found says, "… since all the optical light has been absorbed by intergalactic hydrogen gas, leaving only infrared light." I'm thinking the expansion of space is a more likely explanation...
  15. U

    Communication through cables and optical fibres.

    Hi, I'm in the first year of my engineering course and I've only completed the first four months of the course. As you can imagine,I don't have a very good grasp over my subjects yet,but I'm trying really hard! In our physics syllabus,we have a few things about communication through coaxial...
  16. B

    Optical Phenomena with White Wine and Glass

    Hey all, I went to my 10 year HS reunion party last night, and took about 125 photos using my Sony Alpha 350DSLR, a kit lens, and a Promaster hot-shoe flash. The camera was set to manual exposure of 1/10th sec to allow the ambient light to fill in the background, while the flash was left on...
  17. R

    Resolution of optical binaries

    Imagine a double star with components separated by 10 astronomical units (10 AU). How far away can such a system be while remaining resolved with a 300 mm telescope? Show workings and give your final answer in either light years or parsecs. (Ignore atmospheric effects). Thanks.
  18. W

    Optical Spectra of Helium & Other Elements

    Homework Statement The following elements should have optical spectra similar to either a hydrogen atom or a helium atom. Indicate which of the following elements should have optical spectra similar to a helium atom. (Select all that apply.) The choices are: Cadmium, Lithium, Technetium...
  19. ZapperZ

    What Causes Reflection and Transparency in Solid State Physics?

    We have very frequent questions regarding the "microscopic" details of the process of reflection, the cause of transparency, etc. in solids. In many cases, people often still think of this as being caused by "atomic transition", neglecting the fact that these are solid state physics and not...
  20. G

    Bonding force of an optical electron and the nucleus of ion Cr3+

    Does anybody know how to find bonding force of an optical electron and the nucleus of ion Cr3+ (in pink ruby during normal and excited states (excitement of light))? And also how to find the magnetic moment of the same electron during EPR (during excitement by a radiowave)? Condition of the...
  21. G

    Optical Properties of Materials

    Homework Statement Which of the following oxide materials when added to fused sillica (SiO2) will increase its index of refraction: K2O, Na2O, CaO, BaO? Why? Ionic radii of the ions: K+: 0.138 nm Na+: 0.102 nm Ca2+: 0.100 nm Ba2+: 0.136 nm Si4+: 0.040 nm O2-: 0.196 nm Homework...
  22. E

    How Does Fourier Domain OCT Extend Interference Beyond Coherence Length?

    Hello, I don't know if anyone is familiar with OCT, but my question is rather specific and a well explained answer is in my opinion nowhere to be found ... In OCT, a low coherent light source is used in a simple Michelson interferometer setup. One beam (reference beam) is sent onto a...
  23. G

    Why does a high optical carrier feq. provide higher transmission rate?

    For example , optical carrier in the infra red region can provide higher capacity than microwave.
  24. K

    Optical Theremin - Photocell Question

    I was endeavouring to build the (almost, at least) Theremin on this page: http://www.popsci.com/diy/article/2008-04/build-pocket-theremin-cheap However, I was wondering what kind of resistance the photocells should have. I suppose I could work up a better abstract understanding of the...
  25. H

    Sun Setting Illusion: Explaining Constant Angular Speed

    So I was watching the Sun set the other night, and I noticed that the Sun appeared to accelerate into the horizon. If the Earth rotates at a constant angular speed, how could this be? I was thinking about swinging a ball on a string vertically, and how the ball would have different points of...
  26. K

    Optical transition rate for quantum wells

    So, let's say that you wanted to find the optical transition rate between subbands for electrons in a quantum well. To a good approximation, you can say that the wavefunctions are of the form \Psi = \psi(\vec r) u_c(\vec r) where u_c is the Bloch function and the lowercase psi is a...
  27. J

    Optical mouse into pen tablet. How?

    Does anyone know by any chance or maybe know where to look for a guide instructing you how to make a pen tablet like this out of an optical mouse?
  28. O

    Optical Instruments I: Optical Element

    Homework Statement In the 7 diagrams below, the solid arrow represents the object and the dashed arrow the image. The rectangle shows the position of an SINGLE OPTICAL ELEMENT. Match each diagram with the appropriate optical element. 1)http://img190.imageshack.us/img190/5176/92585723.gif...
  29. A

    Optical Question: HeNe Beam Through Potassium Permanganate

    I am shining a HeNe beam into a 1:1 solution of 40% HF and 7% potassium permanganate. Potassium permenganate is very dark purple (cannot see visible light throught it). I am shining the HeNe through about 2 millimeters depth of this solution. I was wondering how much of the beam is actually...
  30. F

    Optical phenomena with colliding river rocks

    Today, I was red-necking it up with some friends in Auburn at the nearby forest. We found an open area on a decent sized creek that was filled with mostly less-than-fist-sized river rock. After dark, we noticed that when a rock was thrown to the ground (on the other rocks), a small spirt of...
  31. A

    Scattering Problem - Unstable particles and a version of the optical theorem

    Homework Statement Problem: Show that unitarity (of the S-Matrix which has implications to the amplitud of scattering of 2-2 bodies scattering of unstable particles) fixes the numerator of the Partial wave amplitude near the \Delta-pole, q M_1 =...
  32. P

    Optical Theorem: Understanding Conservation of Particles & Probability

    I'm confused. I read a line in a book where there was a qualitative explanation about the optical theorem, namely that it is connected with conservation of particle number. But I think that this is only true if we just consider elastic scattering. Inelastic processes would of course allow a...
  33. O

    Optical Instruments I - Thin Lens

    Homework Statement part1: In the Figure below a lens of focal length 8 cm is placed between a plane mirror and a pin hole. The other side of the pin hole is illuminated by a light source (not shown), so that the light passes through the hole and is then collected by the lens. If the pin hole...
  34. O

    Optical (laser/maser) cooling of fusion products.

    Fusion raction produces high energy neutrons which cause activation of the walls of the reactor. Why can't their energy be collected by, for example, a microwave beam?
  35. M

    Finding a Handy Solution to Measure Variation in Optical Features

    Dear all, I need a suggestion for my work. I have to measure the variation of some optical features of a material in presence and absence of a magnetic field. Hence, I need to “switch on” the magnetic field in a given instant time, to record the signal an then ““switch off”, or even to change...
  36. 0

    Aligning Optical Axis of 2 Lens Assemblies

    i have two optical lens assemblies performing separate functions individually. Now I want to allign their optical axis .. how do i achieve the alignment? (actually i want to allign them back to back and ensure that their optical axes are concordant, if not overlaping ,then atleast parallel )
  37. B

    Optical Density of Compound X: Calculate Molar Extinction Coeff.

    Homework Statement In an experiment it is found that the optical density of a solution of compound X was 0.7 when measured at 400nm. in a 1cm glass cuvette. The solution had been prepared by dissolving 35mg of X in 50 ml of water. What is the molar extinction coefficient of X at 400nm...
  38. G

    I don't remember the name of this optical device

    Hi, time ago I found some Youtube videos and a website about this kind of device made of mirrors that invert the light coming from an object, and the effect (even if I don't remember precisely) should be to disrupt the sense of depth. This is a quickly made illustration of this device...
  39. R

    Help with Exam Question on Optical Position Encoder

    Hello everyone, I have an exam in a few days and need help with a question on one of the past exam papers. An optical position encoder used on a robot axis has a 10:1 gear ratio, an optical disc with 72 slits, and a 12 bit binary counter. Determine: (i) The resolution of the encoder i.e...
  40. F

    Optical problem concerning space mirror.

    When designing a space based energy satellite for our project, we ran across the option to just use a mirror to reflect extra light to a photovoltaic ground station on earth. The main difficulty of this option is that due to the fact that the light coming from the south pole of the sun hits the...
  41. D

    Exploring the Band Model: Optical and Electronic Properties of Solids

    Show how the band model can explain the relationship between the optical and electronic properties of solids? any ideas one were to start looking? lost with this question
  42. T

    Star light extinction and optical extinction

    Homework Statement The normalized extinction is defined as F(\lambda) = \frac{A_{\lambda}-A_v}{A_B - A_v} where A_{\lambda} is the extinction (in magnitudes) at wavelength \lambda . B and V are wavelength bands but for the purposes of this question we will assume that they represent...
  43. P

    How to Calculate Optimal Thickness for Thin-Film Optical Coatings

    Homework Statement A jewelry maker has asked your glass studio to produce a sheet of dichroic glass that will appear red (wavelength=692 nm) for transmitted light and blue (wavelength=519 nm) for reflected light. If you use a MgF2 coating (n=1.39), how thick should the coating be...
  44. W

    Lenses and Optical Instruments

    1. A diverging lens with a focal length of -14 cm is placed 12 cm to the right of a converging lens with a focal length of 18 cm. An object is placed 33cm to the left of the converging lens. Where will the final image be located. 2. 1/f = 1/di + 1/do dob = L - dia 3. After solve...
  45. F

    Optical Path Length Difference & Constructive Interference: Normal Incidence

    Homework Statement Light falls at normal incidence onto a transparent film on a substrate as shown i. what is the optical path length difference in the case of normal incidence? ii. if nf>no and nf>ns, what is the condition for constructive interference in the case of normal incidence...
  46. W

    Optical dipole trap for bec

    optical diple trap is used to trap spinor bec i have a question why are the three different atomic internal levels feel the same shift? To calculate the energy shift of a specific internal level, we need to find out the coupling between this level to higher levels. For different levels...
  47. 0

    Optical light transmission through a coating

    If I was to measure the transmission of light through a coated piece of glass(with a coating designed to scatter light). Do I expect the optical transmission to be different if the light is incident upon the coated side compared to if the light is incident on the uncoated side and exits through...
  48. A

    Experimenting the Speed of Light with Optical Fibers

    I did an experiment on the speed of light with different length of optical fibers. I know that the fiber has a refraction index of 1.49. I would like to know if I need to take in account the total internal reflection of the optical fibers too. Because when I use long fibers like for exemple...
  49. L

    Optical polarization conversion

    From a classical perspective, linearly polarized light can be converted to circular by introducing a phase shift between the orthogonal modes. Could someone give me an explanation of how this works from a quantum mechanics perspective, starting from the fact that each photon has angular...
  50. L

    Conceptual question regarding resolving power of optical instruments

    I've been wrestling with this problem for a while, and I really cannot understand it. As I understand it, the limit of the resolving power of the eye is related to diffraction: when Rayleigh's criterion is just satisfied, then two objects which are close together can just be resolved, i.e. we...
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