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. S

    Optical Fiber Attenuation for 1550nm FBG Sensor

    what could be the attenuation for optical fiber used in fiber Bragg grating sensor with a operating wavelength of around 1550nm
  2. G

    Optical Engineering - Lasers

    Homework Statement Consider an amplifying medium, composed of homogeneous broadening four-level atoms as show in figure 26.5, page 557 of textbook. http://img689.imageshack.us/img689/6108/lt2f.png Amplification is to occur on the 2-to-1 transition. The medium is pumped by a laser of...
  3. M

    Optical setup: proper lenses selection

    Dear all, I am going to realize an experimental optical setup and I need your suggestions to make the correct selection of lenses. A polychromatic light beam coming from a monochromator (400-700, slit dimension: 1 mm, cone angle 11°) has to be focused onto the base of a cylindrical lens. I...
  4. N

    Optical design: BPP beam parameter product M^2 and beam expander

    We work on optical simulation where we use not ideal beam expander. Not ideal means that for beam expander designed for single mode (M^2=1), the output beam has M^2 >1 (M^2 = M squared) In our system we want to use beam expander with multimode laser beam. The beam expander is not ideal (for...
  5. S

    Calculate optical power output of LEDs

    Hi guys, I have to calculate de optical power output of a set of LEDs. For that I used a photodiode to measure the photocurrent at each wavelength and then calculate the optical power at each wavelength using the following formula: R (A/W) = I/P, where R is the responsivity of the...
  6. P

    Description of optical tweezers: Ponderomotive force?

    It is mentioned that in optical tweezers the dielectric particles are attracted to the gradient of the laser's electric field. Is this mechanism the same as the ponderomotive force? If so, why is this connection not made directly? Thanks
  7. M

    Understanding Optical Path Difference in Optics | OPD Explained

    SOme one help me with the OPD. How is here the OPD=n2(AB + BC) -n1(AD)? I am not confused with the introduction of 'n'..Rather the path length is confusing me..Why is there a negative sign?
  8. T

    Optical Activity/Polarimetry

    Hi, I am a 17 year old college student from the UK carrying out an experiment to build a polarimeter to determine the specific rotation of sugars. However, I have a problem when I shine polarised light through my sucrose solution and turn the analyser polariser filter I see colours ranging...
  9. S

    Optical scope for general purpose

    Hi, I'm interested in doing small projects for curiosity. I'm designing an optical structure as shown below. Please tell me what kind of lenses (concave, convex, plano concave etc.. ) to be used at different points of the structure.
  10. V

    Difference between Optical and Geometrical length?

    Difference between Optical and Geometrical length!? I'm having this question since 2 times now in the theoretical part of the exam & still I couldn't find anything about it in the book neither in google. Can anyone who's more experienced in Optical Physics give me the answer to this please !?
  11. G

    Snell's law and optical filters.

    Hi, I recently did a experiment in which I measured the intensity of light out of a optical filter at different angles of incidence. The optical filter was designed such that only light of wavelength 405 nm is transmitted. The wavelength of incident light (the laser I used) was 402 nm. My...
  12. A

    Optical and acoustic modes

    Basically phonons in crystals can either be acoustic or optical according to my book. But then it stresses that a necessary condition for this to hold is that the crystal has more than atom per primitive basis. The optical modes are then when neighbouring atoms oscillate out of phase (i.e. no...
  13. A

    Exploring Waves in Crystals: Acoustical & Optical Branches

    My book considers waves in crystals. Especially it develops the idea of acoustical and optical branches of the waves. From what I can see these are different ways the dispersion of our phonon may look like. It is developed when the crystal contains more than one atom per unit cell, but I am not...
  14. C

    Optical Instruments two lenses

    Homework Statement A 2 cm tall object is 20 cm to the left of a lens with a focal length of 10 cm. A second lens with a focal length of 15 cm is 30 cm to the right of the first lens. Calculate the image position and height. Compare with ray-tracing. Homework Equations 1/f = 1/do + 1/di, m =...
  15. EagleOnePro

    Optical Sensor On/Off for 12V 3.6A Battery

    Hi all I would like some ideas and pointers on how you think that I could drive my electromagnet to turn on/off with some form of optical sensor. I’m using a 12V 3.6A battery. I’m not too knowledgeable in the optical sensor arena. So if you have any ideas on how I could drive this inductive load...
  16. N

    Is This Compound Optically Active?

    Homework Statement Is this compound optically active or inactive?? Homework Equations The Attempt at a Solution This compound doesn't have the plane of symmetry.So according to me it should be optically inactive.is it right??
  17. A

    Exploring the Kerr Optical Effect: λ & E Parameters

    I'm wondering about the Kerr Optical effect as described on wikipedia: http://en.wikipedia.org/wiki/Kerr_effect Are there limits to the range of parameters at which the effect starts to break down? What λ values and E values does this formula apply to?
  18. S

    How does optical density relate to mass density and refractive index?

    Hello I am preparing a lesson on refraction and I've come across a confusing point. In a book I have read, it was said that the optical density of a material is proportional to the refractive index. That is, the greater the optical density, the greater the refractive index. I have however...
  19. S

    Diverging lens problem -image should be between focus & optical centre

    Homework Statement Problem: An object 2.0 cm high is placed in front of a diverging lens of focal length 1.8 cm. The object is 2.7 cm from the optical centre of the lens. Questions: 1) Where is the image located with respect to the focus and the optical centre of the lens, qualitatively? 2)...
  20. T

    Voltage Gating & Microscopic Observation for Measuring Optical Properties

    Hi, I'm wondering if there's any possible way to do voltage gating to a sample while observing it with a microscope, in order to measure its optical properties while changing its electrical parameters. Thanks
  21. G

    Optical rotation and linear basis set

    If I have a 45 degree linear polarized light which I then circularly polarize using a 1/4 wave plate and put this through an optical rotary crystal and then using the equivalent 1/4 wave plate but in the reverse oriention, will I get back a 45 degree linear polarized light? Put another way...
  22. H

    Simulating diffraction in optical instruments - help settle a dispute

    Consider a Newtonian reflector telescope: As you can see in the image, the little secondary mirror inside the main tube is supported by an X structure called 'spider'. The four "legs" of the spider, called 'vanes' by astronomers, are actually thin stripes of high-tensile material, usually...
  23. N

    Breaking the coherence of an optical signal

    Hi, I am curious to know if there any passive (or simple active) methods to convert a very coherent signal into an incoherent one? I suppose I would need to find a way to chirp the signal and a non-linear medium might be one method. Any ideas? Thanks narra
  24. N

    Optical Gian vs Electrical Gain

    Hi, I was wondering what the trade-offs were in having an optical gain (say with EDFA) compared to electrical gain (say with a PIN and transimpedance amplifier) of an optical signal. Thanks.
  25. J

    Measure optical power with spectrometer

    Hi all, I have only one spectrometer and 2 different light sources. I need to measure the optical power of the light sources. The spectrometer has a resolution of 8 nm. I measure the spectrum of each light source. And then calculate the optical power by integrating over the spectrum. My...
  26. T

    Ray tracing through optical system of thick lenses

    Can you advise me a free software that allow to draw rays passed throught system of thick lenses (preferable in 3D)?
  27. N

    A question about optical theorem

    Optical theorem says that total cross section proportion to elastic scattering amplitude in the forward direction.Then if the target is absolutely reflective ''mirror''(in the case of quantum mechanics:scattering potential=infinity(r<a) and de Broglie wave leng limits to 0),in this case the...
  28. S

    Optical Fibreglass: Composite Material

    If you had to classify the above material under one of the below material categories which would it be? a) Ceramic b) Composite c) Metallic d) Polymer.
  29. B

    Uncertainty principle regarding a narrow optical fibre?

    If we take a narrow aperture(such as the one used in the double slit experiments) and attach a length of optical fibre to it, surely now we know the position (confined by the width of the fibre) and also the momentum(defined by the direction of the fibre). How does the uncertainty principle...
  30. A

    Acceptance Angle in Optical fibre

    According to the derivation of acceptance angle the first step is, The condition for Total Internal reflection(TIR) is sin(i)≥n2/n1, where i is angle of incidence in the core, n2= refractive index of the cladding and n1=refractive index of the core. sin(i(c))=n2/n1, where i(c) is the...
  31. H

    The big bang's optical paradox

    Optics would predict that objects appear bigger in size as higher the redshift and the density should be the same independent of the galaxys redshift. As far I know this is not supported by observations. Anybody has an explanation please? sdgs_cat
  32. T

    What is the relation between Ultra-cold atom and optical lattice?

    Ultra cold atom is achieved by laser cooling. For optical lattice, it is achieved by the interference of counter-propagating laser beams. What is the relation between Ultra-cold atom and optical lattice? Why do people load Ultra-cold atom in optical lattice? Thank you for your answer.
  33. K

    Engineering Pros and cons of photonic and optical engineering

    I 'm thinking to study about photonic and optical science, I always like the property of light and I want to study at the university Arizona. I want to know what is the good and bad side of this career because I am deciding, am I choosing a right career? Thanks.
  34. J

    Optical waveguide modes with different speed, what happens?

    Hi, I'm new on the forum and I would like to start with a question. I've searched for a reply in old posts with no success. If you can help me to find an answer I'll be very glad. Talking about optical modes inside a waveguide. If a waveguide support two different modes, say TM and TE mode...
  35. D

    How does optical reflection work?

    How does reflection work in non-metals and metals? If you take, for example, a polished brass surface (or whatever really) and an incident photon, is the photon being absorbed and re-emitted by an atom at the surface of the reflective brass? If so, how is it that the re-emitted photon is...
  36. E

    Understanding Optical Modes Without the Jargon

    What is an "Optical Mode". I've been reading a lot of solar cell articles, especially those having to do with nanophotonics. There is a term that I keep running into, 'optical mode', but I've yet to find an explanation that I can visualize or understand. What exactly is the "mode" being used...
  37. G

    What makes SiO2 an excellent cladding material for optical fibers?

    can anyone please explain this property of silicon: An excellent oxide as the low-refractive-index cladding material. thanks
  38. D

    Optical tweezers, QPD back focal plane interferometry vs imaging

    Hello, I use a 10x infinity objective as a condenser in a optical trap setup. The collimated forward scattered light is then focused with a 40mm lens onto a QPD. This is the imaging techqnique. There is also BFPI, and I am not clear on this method. My understanding is that I need to image the...
  39. D

    Optical trap Raman - oil refractive index matching

    I have a Optical trap that collects Raman. With Glass cover-slips we use a 1.51 refractice index oil (DF cargille). The trap works but glass has high auto-fluorescence at our excitation wavelength(785 nm9), the weak Raman can't be detected. So we use synthetic fused silica cover-slips with a...
  40. denjay

    Engineering Optical Engineers: Career Info & Job Prospects

    So my Google skills must be getting rusty because I can't find any good information on what Optical Engineers exactly do. I've narrowed it down to design optical systems.. and that's about it. I don't know the job prospects (are they in demand? are they too niche?). I don't really know what...
  41. Ascendant78

    Why Is My New Optical Prism Not Showing a Clear Spectrum?

    I am trying to gain a better understanding of physics outside of my classes. As such, I decided to buy myself an optical prism to learn more about the spectrum of specific light sources, light filtering, etc. I just received my prism in the mail today, but am severely disappointed. When I was...
  42. T

    Infinite Square Well for Bosons in an optical lattice

    I'm working on a research project and was wondering what you could use to experimentally create a periodic infinite square well (dirac comb?) in a direction orthogonal to a different potential, say a periodic potential. To help you understand what I'm trying to do picture a grid of atoms and...
  43. R

    Textbook for Structural Geology and Optical Mineralogy

    Hi guys, Please suggest a good introductory books for Structural Geology and Optical mineralogy, thanks :)
  44. J

    Why can't optical phonons travel far?

    I can't figure this out/find the answer. Why are acoustic phonons very low loss (i.e. earthquake P and S waves), but optical phonons die out rapidly? Thanks, Joel
  45. U

    Question regarding optical isomers

    Homework Statement We know that all meso compounds are optically inactive but is the reverse true? Are all optically inactive compouds meso?
  46. E

    Is this 43mm Digital Camera Lens Made of CdTe?

    Hello everyone! What materials are used for making optical filter glasses? I bought this: http://www.alibaba.com/product-gs/495852853/Digital_Camera_lens_43mm_950nm_IR.html and took its transmission spectrum. So, it reminds me a transmission spectrum of CdTe. But a-CdTe is more...
  47. Strilanc

    Can the result of an optical circuit depend on when you check it?

    I'm trying to understand how optical circuits behave. In particular, if they can interfere "across time". Consider this optical circuit: Suppose that it is completely isolated from the outside world (until we check it), and that the detectors are time-insensitive (they record IF a photon was...
  48. D

    Direct and Indirect Optical Band Gap

    I've been looking on journals and textbook, as well as internet. Does anybody know if there is an equation to find out the value of direct optical band gap and indirect optical band gap? What is the difference of optical band gap, direct optical bandgap and indirect optical bandgap? also...
  49. R

    Why Does a Ray of Light Not Get Refracted at the Optical Center of a Convex Lens?

    I'd like to know why a ray of light passing through the optical center of a convex lens does not get refracted at all. According to my knowledge, a ray of light will not get refracted if the angle of incidence is zero i.e. it is along the normal. With this in mind, I see how a ray traveling...
  50. I

    Calculating the Optical Rotation Value

    Homework Statement So the problem states that we have a (+) enantiomer of a coumpund with an optical rotation of 50*. If a pure sample containes 42% of the (+) enantiomer and 58% of the (-) enantioimer, what is the optical rotation value. (By * i mean degrees) Homework Equations I'm not...
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