Optics Definition and 999 Threads

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. R

    I Beam-splitter transformation matrix

    The transformation matrix for a beam splitter relates the four E-fields involved as follows: $$ \left(\begin{array}{c} E_{1}\\ E_{2} \end{array}\right)=\left(\begin{array}{cc} T & R\\ R & T \end{array}\right)\left(\begin{array}{c} E_{3}\\ E_{4} \end{array}\right) \tag{1}$$ Here, the amplitude...
  2. C

    How can I derive Eq 9.5.11 in Scully's Quantum Optics

    Firstly, I don't know in which Picture this equation holds (if I hadn't missed some words in the previous text...). I think it may be the Heisenberg Picture. But if it is, the rest target is to prove $$\frac{i}{\hbar}[H_R+H_{FR},(a^\dagger) ^ma^nO_A]=\langle\frac{d}{dt}((a^\dagger)...
  3. D

    Interferometry (testing of optics)

    Hi all, I'm a mechanical engineer who has been dumped into optical metrology at work without anybody much more knowledgeable than myself to help me out. A previous mentor who left recently (who was our optical expert) always told me when measuring wavefront error of optics to "tilt-out the...
  4. Andy Resnick

    New Optics Toy: A 'Varicolor' filter

    Spike Walker, whom I semi-regularly consult with about my Ultraphot III, recently told me about a really cool optical device: a 'Varicolor' filter, manufactured (and discontinued) by Cokin. I found one for $10 on eBay, received it yesterday, and I can't put it down. Here's a set of images of...
  5. R

    Frequency to temporal period conversion

    I am working with signals that look like the following. The curve has the same form in both frequency and time domain. I am trying to calculate the ratio of two distances: The distance between two adjacent red "x"s (known as the free spectral range (FSR)). The distance between two adjacent...
  6. mikenw

    Curious optical effect related to light passing through a mesh

    I hope someone here can explain this curious light effect! Some background: I have a table with a laptop on it, and a chair sitting at this table that has a mesh back on it that has a pattern of ~2mm holes cut into black material in a regular pattern. I happened to notice one day that I could...
  7. Chestermiller

    Possible to prove mathematically that the football spot was bad?

    In the 2016 Michigan vs Ohio State Football Game, the referee spotted the ball after 4th down with seconds to go in the game with what appeared to be a "bad spot." If not for this, Michigan would have won the game. On the next play, Ohio State scored a touchdown that won the game. Would it...
  8. Adgorn

    Rayleigh criterion when light phase is known

    Hi everyone, this is sort of a soft question which I need to ask to make sure my understanding is correct, it relates to a little project I'm doing on measurement resolution. The first question is to clear up a general concept, the second is based on the first and is the actual question...
  9. Seanskahn

    Are there still open problems in classical wave optics?

    I have been revisiting my notes from my 2nd and 3rd year physics degree - especially the ones covering Fourier Optics, and other classical wave optics - and it is quite rewarding to revisit the historical / exploratory aspect of the series of discoveries, that built the foundations of this...
  10. M

    Numerical aperture of a Keplerian telescope

    Homework Statement [/B] Design an afocal Keplerian telescope to imagine an object of ##L = 5\, mm## with a resolution of ##R = 2\, \mu m## and a magnification of ##M=-2##; assume that the wavelength is ##\lambda = 500\, nm##. Don't use lenses faster than ##F/1##. Using the optical invariant...
  11. TachyonLord

    Why Are My Newton's Rings Experiment Results Inconsistent?

    When monochromatic light is incident on a plano convex lens(as shown in the picture), these dark rings are produced which are observed with the help of a traveling microscope. The procedure requires us to measure the diameter of each ring (We need to measure the diameter of at least 10...
  12. LarryS

    Principle of Least Action for optics?

    Fermat's Principle states that light always travels the path of least time. In Classical Physics, other than the above, is there a separate "Principle of Lease Action" for light? Thanks in advance.
  13. M

    Fourier transforms, convolution, and Fraunhofer diffraction

    I've been exposed to this notion in multiple classes (namely math and physics) but can't find any details about how one would actually calculate something using this principle: Diffraction in optics is closely related to Fourier transforms and finding the Fraunhofer diffraction of an aperture...
  14. Edge5

    How does photolithography align wafers through opaque layers?

    In a lithography process I have a hard mask which is opaque. I have to make a wafer alignment, however I use optical techniques to align my wafer (lasers etc.) . How can I align my wafer through an opaque layer?
  15. iVenky

    I Single-mode vs multi-mode fiber coupling

    Hi, Is coupling light from a laser into a single-mode fiber (transverse electric) more difficult than coupling to a multi-mode fiber? If so, is it due to the geometry? Does the laser light have multiple modes to begin with or it can be designed to have just one mode? Thanks
  16. Bheshaj

    Wavefronts: Understanding Wave Optics

    What Is a wavefront? How can we interpret it?
  17. universal2013

    Beginning through the Pedrotti optics book -- I have an energy question

    Hello. I started to work on pedrotti optics book (2nd edition) and i got confused about what is relativistic mass and why we use it rather than kinetic energy (1/2mc^2)? Also in the beginning of these explanations there is one equation i barely understand nothing out of it. Could you please...
  18. TachyonLord

    B Whats the principle behind Schuster Focusing?

    I know its something related to the asymmentry in the i-d curve but its still not clear.
  19. G

    Calculate the focal length of the spectacle lens

    Homework Statement A hyperopic eye has a near point of 1.10 m. Calculate the focal length of the spectacle lens required to correct the hyperopia (assume that the near point of the normal eye is 25.0 cm.) Homework Equations 1/f=1/p+1/q The Attempt at a Solution I just used .25 m as p and...
  20. TachyonLord

    Fizeau's Experiment (Speed of light)

    Homework Statement In the Fizeau's Experiment to determine the speed of light, let the gear have N teeth, the frequency of the rotating gear being f, the distance traveled by the light beam/ray L (distance b/w the gear and the mirror) and let there be n eclipses(blocking of the light beam)...
  21. P

    What exactly is the thermal lens effect?

    Hello, i just wanted to ask if you can explain to me what thermal lens effect is? I am supposed to answer why laser beam passing through ink or soy sauce creates this effect and i can't find any information on what actually this thermal lens is. I know of course that it is a lens, but why does...
  22. N

    Received power for free space optics

    Hello everyone, I have calculated the received power for free space optic (FSO) using the equation: Lsystem (system loss) is set to 8dB. PTotal can be calculated as: where Ntx (number of receiver) = 1 and PTx (transmitted power) =7.78 dBm. LGeo can be calculated as: where d2R (receiver...
  23. A

    What is meant by Spectral and Spatial Shaping of a laser

    Hi, I am new to the forum so apologies if I placed this in the wrong subforum though I think the subject is classical enough to be here. I was hoping to get a concise answer to what is meant by spectral and spatial shaping of a laser. My intuition says that we are modifying the amplitude of the...
  24. P

    Reading optics diagrams: Glan-Taylor

    Hi everyone. This isn't for a class but more for lab work. I'm confused on how to read optics diagrams to understand this Glan-Taylor prism, specifically the up and down arrow vs the dot. Does the arrow pointing up and down mean that it is vertically polarized. Is the dot horizontally polarized...
  25. N

    Optics to act as a mirror or transparent medium depending on incident angle

    I am looking for an optical piece that can act as a mirror when the angle of incidence is close to normal (90 degrees) but acts as a see-through glass when the angle of incidence is less than 60 degrees? Alternatively it can be a filter placed in front of a mirror that passes a lot of light at...
  26. C

    Is this the simplest optical cloak possible?

    https://www.researchgate.net/publication/273269952_A_Simple_Unidirectional_Optical_Invisibility_Cloak_Made_of_Water Why did the authors of this cloak not choose a system with only three refractions for each light ray, so that the cloaked area would be a parallelogram? Is this impossible, or...
  27. ThomOnTheBus

    Optical effect seen on a bus: mirrored screen shows different colors

    Hello Physics People, i was on bus 59 lately and i noticed a typical optical effect. There is a monitor/screen in the front of the bus that lists the current and coming stops and updates when you pass one. Its colour scheme is was blue/lightblue/white (see first picture). But when i looked at...
  28. A

    Question regarding Ray Optics and Probability

    Let there be a sphere whose inner surface consists of a perfectly reflecting surface. It has a hole on it which allows a ray of light to enter. Give the angle made with the normal of the hole when the ray of light enters such that the probability that the ray comes out is the least?Assuming the...
  29. W

    Intensity of Interference Pattern

    The Attempt at a Solution The solution I keep coming up with is (G) , but the solution sheet says it is (C). I assumed it was (G) because since the slit width is halved the central maximum is bigger so I assumed that X would now be part of the central maximum. Therefore the intensity would be I_0.
  30. DariusP

    Self-phase modulation question (nonlinear optics)

    Okay, so SPM (self-phase modulation) is an effect that happens when an ultrashort pulse travels through a medium and it leads to a change in that pulse's frequency spectrum. It is explained that it occurs because an ultrashort pulse somehow induces a varying change of refractive index and this...
  31. I

    Geometrical Optics - Light ray angles on a spherical mirror

    I can't see how the textbook produces the following relationships between angles: $$ \theta = \phi + \alpha \qquad (1)$$ $$ 2\theta = \alpha + \alpha ' \qquad (2)$$ My thinking is that the exterior angle theorem for triangles was used to create expression ##(1)##, but I am unsure as to how...
  32. A

    B What easily avaible liquids are transparent in IR?

    Hi I want to make a infrared nonimaging concentrator, but since crystals needed for lenses are difficult to work with for an amateur, want to use liquids. I am interested in the 1-12 micron spectrum; what liquids could i use?
  33. CDL

    Mean Frequency and Frequency Spread of a Laser Pulse

    Homework Statement Laser probes are being used to examine the states of atoms and molecules at high temporal resolution. A laser operating at a wavelength of 400 nm produces a 1 femtosecond pulse. Compute the mean frequency and frequency spread, ∆ν, of this laser pulse. Homework Equations c =...
  34. A

    "Total" destructive interference of plane waves

    Hello. Let's suppose that we have a Michelson interferometer to study interference patterns of light. This time we use plane waves. If we set the whole thing up so that the two separated beams have a phase difference of π when they superpose, destructive interference ensues. Since we're...
  35. Beth N

    Geometric optics: Thin lense equation

    Homework Statement A 2.0-cm-tall candle flame is 2.0 m from a wall. You happen to have a lens with a focal length of 32 cm. How many places can you put the lens to form a well-focused image of the candle flame on the wall? For each location, what are the height and orientation of the image...
  36. M

    Frequency of Differently Coloured Light

    We know that light of a specific colour has a specific frequency. Suppose we have a torch emitting white light, and we place a, say, red cellophane paper, in front of it. Now we would have red light. So does this mean the new beam we get has a new frequency? How?
  37. astroman707

    I What areas of nano/optical research applies to astrophysics?

    I'm an undergraduate and there is a very good optical spectroscopy and nano-materials physics lab at my college. I have FULL access to all equipment and a professor in that field is offering me a ridiculous amount of co-research time during the school year. However, I'm really only interested...
  38. N

    I How to estimate total energy when dealing with beamsplitters

    I'm having a brain freeze right now and I need some help. :frown: I have a 50/50 beamsplitter (non-polarizing) with 5% tolerance. Test measurement (with a laser at a certain wavelength) gave that I'm transmitting 5.36 units and reflecting 4.6 units (49.5 transmitted; 42.6% reflected). Units...
  39. K

    Optics: Huygens' principle and bending of light

    I know the technical details of why light bends towards "the normal" when meeting a more refractive medium must be complicated. But I was thinking about it in a more lay fashion. I was thinking if the bending can be explained using Christiaan Huygens' principle in that a light front is made of...
  40. B

    Sanity check: Using the Jones calculus for superposition

    Homework Statement Suppose light is prepared in a coherent superposition of linear horizontal polarization and linear vertical polarization. What is the resulting polarization according to Jones calculus if it passes through: a linear polarizer at a 45-degree angle (0 degrees would be...
  41. J

    How do I find the refractive index in sugar solutions?

    For class I conducted a experiment where I made sugar solutions, poured them into a glass prism container and used a laser pointer to find the refractive index. However, while typing in my results I realized I found the angle of deviation instead of the minimum angle of deviation since I didn't...
  42. T

    A question about optics: Why does a pinhole aperture work like my eyeglasses?

    i wear glasses to correct my out of focus vision. Without glasses everything is slightly out of focus. Quite by accident I looked through a tiny pinhole about the size of a pinprick without my glasses using one eye. To my amazement everything was perfectly sharply in focus. The same with...
  43. C

    Is there refraction upon frustrated total internal reflection

    In frustrated total internal reflection, is there refraction corresponding to the refractive index difference between the first and third medium or does the light continue in straight line as it is usually depicted in graphic representations of the frustrated total internal reflection?
  44. S

    How Does the Fraunhofer Condition Affect Diffraction Patterns?

    Homework Statement A square aperture with a side of length 0.5 mm is illuminated with light of wavelength 550 nm. At what distance from the aperture would the Fraunhofer diffraction pattern have a central maximum with a width also equal to 0.5 mm? What can you say about the Fraunhofer condition...
  45. B

    Phase shift and circular polarization

    What is the phase difference between the right circularly polarized and left circularly polarized light of the same amplitude? And how do you calculate it?
  46. T

    Wavelength of a laser within an optical cavity

    1. The problem statement, all variables and given/known date Homework Equations $$\delta v=\frac{c}{2nL} \:[1]$$ $$N=\frac{\Delta v}{\delta v}=\frac{2nL\Delta v}{c} \:[2]$$ The Attempt at a Solution I am having trouble with question 5, but have come to realize I think my cavity length is...
  47. B

    Optics Experiment involving transmission through a gel and a sphere

    Assume you have the following scenario: Light begins traveling through a gel of index of refraction n=1.34 in a straight line along the x axis. It is then incident on a solid sphere(n=1.36) of radius R in 3-space. Upon transmittance, the light again travels through the gel(n=1.36) and finally...
  48. P

    Studying Textbook suggestions for LiDAR/Radar/RF Telemetry

    Previously I made this post, and soon after realized how woefully unprepared I am to approach such a topic. As stated in the post, I think my best use of time would be to gain background knowledge on the topic before attempting a project, but now I think I've found a better focus as to what...
  49. L

    Geometric Optics Approximation - validity

    How is the "geometric optics approximation" exactly defined? Given all the source of visible radiation's parameters, all the apparatus, instruments, screen, etc, specifications, how can I know if, e. g. there will be diffraction, interference or other wave properties or if I'll be able to...
  50. BillTre

    Optical What are the top DIY optics projects in the Instructables Optics Contest?

    The Instructables website is having an Optics Contest (going for 43 days from now). You could win an iPhone X! These are DIY projects that you write up with pictures so that other people can replicate them. Instructions --> Instructables. There are already several entries you can view there...
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