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. Y

    Study molecular conformation using optical spectroscopy?

    I want to study the molecular conformation of conjugated polyelectrolyte (CPE) using optical spectroscopy. Obviously a lot of people have used optical spectroscopy to study the structure of conjugated polymers, including this conjugated polyelectrolyte. However, they did in when the CPE is in...
  2. F

    Aperture stop for an optical system

    Hello Forum, The aperture stop (AS) of an optical system is that physical aperture in the system that limits the amount of light from the object. Consider a 2D object formed by point objects. The AS is determined by considering the object point that is located on the optical axis. Will the AS...
  3. H

    Simplest lens set up to reveal optical spectra of an object

    I have done basic experiments where a laser is shot thru a grating and a lens is inserted at the diffraction pattern to put the spectra back together and form an image of the grating. apart from this being the single most mind blowing experiment ever to witness I have some questions about the...
  4. Daoyang

    Can I control the lighting of thousands of optical fibers?

    Hi everyone! This is my first post. I hope I am posting in the right place -- if not, please let me know. I am also hoping my question will not sound too absurd; I am no physicist, just someone who would like to use complex technology to create an art installation, and I'm having a hard time...
  5. J

    Optical phonons in fcc-lattice

    Aluminium has an fcc structure, which is a simple cubic lattice with four Al-atoms in the basis. On the other hand, diamond has a diamond structure, which is a simple cubic lattice with 8 atoms in basis. Now, diamond has optical modes in addition to acoustical, while Aluminium does not. What...
  6. D

    Derive the Gunn-Peterson optical depth expression....

    Homework Statement Derive an expression for the Gunn-Peterson optical depth Tau(λ) for Lyman limit absorption from smoothly distributed intergalactic neutral Hydrogen of comoving density n0 toward a QSO of emission redshift zem. Take the absorption cross section for Lyman-limit absorption to...
  7. J

    What is the role of degeneracies in the condition for optical gain?

    I'm a novice studying laser physics and I came a across the condition for optical gain: \frac{N_2}{g_2} > \frac{N_1}{g_1} This is a basic set up where N_1 is the number of atoms in the lower energy state and N_2 is the number of atoms in the higher energy state. g_1, and g_2 are the...
  8. Ornit

    Ion Assisted Deposition (coating technology)

    Hi all, When talking to some of our optics vendors, I got the impression that Ion Assisted Deposition (IAD) is standard. We use our optics at high power densities and we care about laser damage as well as adhesion and density of the coating (aka porosity, helps reduces sensitivity to humidity)...
  9. L

    Acoustic phonon lifetime is larger than optical phonon?

    for example, in GaAs, the LA phonon lifetime can be ~850 ns, while LO phonon lifetime is only about 5 ps. Why such huge difference occurs? Thanks!
  10. X

    The Optical Theorem (Total cross section?)

    I am going over the optical theorem (specifically from Sakurai) and I just have a simple couple of questions. The optical theorem says \sigma_{total}=\frac{4\pi}{k}\text{Im}(f(0)) Where ##f(0)## is the scattering amplitude in the forward direction. (Which I am assuming means the direction...
  11. zambadeos

    Accuracy of an Optical Spectrum Analyzer (OSA)

    Hey! I've a simple (and maybe stupid) question about the accuracy of an OSA. The datasheet report a level accuracy of 0.4 dB but this seems quite strange to me. Indeed level measurements are done in dBm thus, as long as dB measures a relative power, I assume that even the 0.4 dB are referred to...
  12. S

    Change in Optical Path Length

    Homework Statement A thin film of dielectric material of refractive index 1.455 and thickness 6.50 mm is now placed over one of the slits (say the right-hand one). By how much will this change the optical path between the slit and the centre of the screen? Homework Equations Optical Path...
  13. Z

    Is Dark matter an optical illusion?

    The main evidence for the existence of dark matter is the flat rotation curve of galaxies, and high peculiar velocities of galaxies in galaxy clusters. The mass eclosed in a radius R is derived from the Keplerian equation M(R) = v2R/G . Also we know about the existence of gravitational...
  14. Artlav

    Calculating optical properties of an arbitrary gas?

    Hello. Is there a way to calculate properties of a gas, given only it's composition? I.e. let's say i want to know what would a planet look like with an atmosphere of a mix of 50% gaseous sulphur and 50% gaseous mercury, at 500*C and surface pressure of half that of Earth. How would i go about...
  15. I

    Real World Applications of Optical Cavities: What Can They Be Used For?

    Are there any real world uses for optical cavities. Optical (or laser Cavities) description: where lasers continually bounce off two reflecting mirrors.
  16. alanwake90

    Questions about Lock-in detection in optical reflectivity

    Hi guys~ I have a question about lock-in detection method that commonly used in optical spectroscopy experiments, for example, the optical pump-probe reflectivity exeperiments on some semiconductor surfaces, or kinda like that. Usually, the sinario is: you use laser pulses, divided as pump and...
  17. M

    Active Galaxies: Comparing Optical and Radio Astronomers' Perspectives

    Homework Statement Describe what optical astronomers would consider the properties of an active galaxy and also describe what radio astronomers would describe as the properties of an active galaxy and explain how two sets of astronomers came up with these differing conclusions. Homework...
  18. N

    Optical Character Recognition using Neural network

    Hey all, does anyone know a link where I can find a c# implementation of a neural net that does OCR WITHOUT using libraries, I feel that OCR is a nice way to learn how neural nets classify data. Any help appreciated, thanks.
  19. 010101

    Optical Adder Using 2 Lasers & Selectable Intensities

    If we use 2 lasers with selectable light intensities as input, with each level of intensity corresponding to decimal number. Like level 0 intensity - decimal 0 (MIN) level 1 intensity - decimal 1 level 2 intensity - decimal 2 ... level 9 intensity - decimal 9 (MAX) and directly shine both of...
  20. Dan LaSota

    Vendor for Flint Glass Block or Prism

    Hi, I'm trying to put together materials to demonstrate the Faraday Effect. I need to locate the supplier of some flint glass (glass with lead oxide or similar materials increasing the Verdet constant), that I could use in my lab. I had found this from Mansion Schools...
  21. L

    Debug help: optical laser interference setup fails to work

    I’m looking to demonstrate destructive optical interference using a laser pointer. I’m splitting the beam with a prism and projecting the beams onto one point on the wall. Somehow I’m failing to get any effect, however. Setup: 1. I’m using a static laser pointer, a prism and a handheld mirror...
  22. C4l1

    How Can the Euler-Lagrange Equations Describe Light Path in Optical Fibers?

    Homework Statement An optical fiber is one way to guide light efficiently from one point to an other. It is currently used for data communication: it offers low loss and very high bandwidth, ideal for the requirements of the internet. Generally, we can describe an optical fiber as a medium with...
  23. S

    Calculating the distance between the optical center and focal length

    -Hello everyone. At school, I studied about convex lense and concave lense. They are very interesting, we learned about how lights would be after going through the lense. But what I want to ask is how we can calculate the distance between optical center and focal (I means focal length). Focal...
  24. T

    Newton's optical theory of gravity

    Isaac Newton had an optical theory of gravity which you could make work with the light like corpuscles Newton never knew of, namely neutrinos So said my physics Professor once ... I wish there was a forum for discussing Newton's optical gravity theory, I think it could help explain ( the...
  25. Andy Resnick

    Photograph of (optical) caustics

    Caustics are singularities in the optical field: http://en.wikipedia.org/wiki/Caustic_(optics) I took this photograph of caustics created by the sun reflecting off of moving water today- The spatial pattern of spots is related to the (local) slope of the water: Each dimension in this image...
  26. S

    Refraction through an optical fiber

    Homework Statement Given a "new type" of optical fiber (index of refraction n = 1.23), a laser beam is incident on the flat end of a straight fiber in air. Assume nair = 1.00. What is the maximum angle of incidence Ø1 if the beam is not to escape from the fiber? (See attached file for...
  27. V

    Violation in diffraction? Lagrange (Optical) invariant

    It says you can not change with lenses the value L - radiance. Below I have an example where it proves that you can or where am I wrong? (I made L for 2D case, in 3D case everything the same - L2>L1)
  28. Alexi-dono

    Creating a Language for an Optical Computing System

    lets say someone had an idea for a fully optical computer; that had a optical cubic processor, that refracted and reflected signals. into a optical "motherboard" (except it was not a flat board, more of a rectangle), how would one go about writing a language for such a thing (lets say a base 8...
  29. O

    Testing Low Pass Optical Filter

    An optical low pass filter is supposed to blur the image using birefringence. I took out an optical low pass filter from a digital camera where it is used for anti-aliasing purposes. The filter looks just like a piece of glass. I pass a diode laser beam through it and look at the beam spot on...
  30. D

    Comparing Optical Signal Power with RMS Voltage

    I have a CW laser system, the optical detector receives a pulse width modulated signal and converts it to an analog signal. Both the source and detector have 32 channels and I would like to know what the analog signal power is, I thought maybe I could use the RMS voltage received on the...
  31. R

    Focal length of the optical system

    I understand this that when an object is kept at focus of convex lens, then image is formed at infinity. So when we keep a convex lens above plain mirror and move object needle on the principal axis of convex lens and see a coinciding image with needle on lens and measure distance from lens then...
  32. D

    Perturbing Hamiltonian optical absorption in semiconductors

    Hi I am looking at the problem of optical absorption in direct gap semiconductors. It seems like the perturbing Hamiltonian is an oscillating perturbation , ie. an electromagnetic wave. Why can't the problem be treated as the absorption of a single particle , ie. a photon ?
  33. K

    Optical system & diffraction limit

    can you please let me know if this sentence is true about optical systems or not? "Diffraction may limit the resolution achivable by an optical system" Thanks.
  34. W

    Optical System with Diverging Lens and Concave Mirror

    Homework Statement A diverging thin lens and a concave mirror have focal lengths of equal magnitude. An object is placed (3/2)f from the diverging lens and the mirror is placed a distance 3f on the other side of the lens. Using Gaussian optics, determine the final image of the system after two...
  35. Domenico94

    Solar panels and optical parametric oscillator

    Hi everyone. On these days, by watching solar panels and similar stuff, I just thought about it, and why they take such a wide surface to produce energy, and why their output is often low, as we all know. By navigating here on the internet, I've just seen a device called OPO (Optical...
  36. S

    Imaging CDs, DVDs or other optical media under SEM

    Greetings, After getting some training I have access to my universities SEM facilities and I would like to image CDs and DVDs with it(, I know that these consist of many layer which may not be transparent to the e-beam so they might need some preparation. Does anyone have any idea? I am...
  37. C

    What Causes Optical Density in Media?

    Which property is responsible for optical density In media
  38. O

    Hand drawn ray tracing through an optical system

    Hi, I am familiar with drawing rays through a lens. But when a few lenses are put together, things become confusing to me. For example, if a first positive thin lens at 0 forms a real image 10cm away, what would happen when we put a second positive thin lens, say at 5cm along the optical...
  39. S

    Number of bits per pulse width in buffers and delay lines (optical)

    Hi I was working on delay-lines and I wanted to know if a pulse is delayed by 10 pulse lengths through a delay-lines than what is the corresponding storage bit for that delay line. Thanks
  40. S

    Optical Fiber Link: 1500Km, 10Gbps NRZ

    Homework Statement [/B] Below is the original question and I just want to check out my answer of part one only. A single mode optical fiber link is required to link two major cities that are 1500 Km apart. The link must be capable of transmitting a minimum (NRZ) data rate of 10Gbps. The...
  41. E

    Find the Frequency Spectrum of an optical communication link

    Homework Statement 2. Homework Equations 10 Log[10](g/mW)= GdBw The Attempt at a Solution I have attached a document of my approach to this question. I would like to know if my approach is correct? Thank you for your assistance
  42. hideelo

    Understanding Stability Conditions for Unsymmetric Optical Resonators

    I am trying to understand the conditions for an optical resonator with unsymmetric reflectors, i.e. the focal lengths of the two reflectors are different. According to wikipedia (http://en.wikipedia.org/wiki/Optical_cavity#Stability) 0 < (1 - L/R1)(1 - L/R2) < 1 is the equation that will...
  43. X

    Optical Noise Photons: Calculate Sun's Ambient Light for Detector Simulation

    I need this information for a simulation I am working on that involves optical photon detectors. Specifically, I need a rough figure for how many photons a photon detector would register per second if I were to place it in ambient light from the sun. I realize that this number depends on the...
  44. P

    Any good softwares for drawing optical schematics?

    Hi all, Are there any good softwares for drawings schematics like this? I need to make and insert such images in my thesis report.
  45. RoundEarVulcan

    Optical drive SSD conversion Mac

    Hi guys, I was just wondering if any macbook pro owners have successfully converted the optical drive into an area to hold an SSD. I am planning on keeping my current HDD and adding the SSD. Please let me know how it went and how much it affected the performance. (2012 MacbookPro non-retina)...
  46. W

    Degeneracies in Optical Modes in relation to Heat Capacity in a Solid

    Technically I'm supposed to have a total of 8 optical modes but only 4 of them were seen in a solid (by spectroscopy). So I suspect there's some degeneracies and symmetries involved, but I don't know which ones. I have two sets of assigned degeneracies: frequency; degeneracy set 1; degeneracy...
  47. F

    What is the range of optical frequecy?

    I see the term o"ptical frequency" in some articles. From Wikipedia I read that it means the whole EM spectrum. But something says to me it may be only the visible part of the spectrum. Now, which definition is correct? Thanks
  48. phoenixXL

    Solving CycloHexane Isomerism: Find Total # Possible Isomers

    Question Find out the total number of possible isomers with molecular formula C6H12 that contain a cyclobutane ring. Attempted Solution In Compound 3, Optical Isomerism is possible (geometrical isomerism is also possible but is neglected due to presence of optical isomerism) about both the...
  49. Z

    Efficiency of non-linear optical device

    It is said that a non-linear optical device may convert light into its higher order components. So what is the highest efficiency of the conversion? Can a non-linear device convert all input light into its higher order frequency? Thanks.
  50. W

    Relating molecules, atoms to number of optical branches (modes)

    I'm stumped as to how many optic branches (modes) are present if there are X number of molecules in a unit cell and Y number of atoms in each molecule. I know that each individual atom has 3 degrees of freedom and more generally in a single unit cell, there are 3 acoustic branches (modes) and...
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