What is Optics: Definition and 999 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. F

    Microscopy magnification problem

    Hello, I'm having trouble understanding how and why the math is the way that it is to get the answer. The question states: A specimen has a diameter of 1.5 micrometer. What is the minimum magnification that will allow a human to resolve this object? 150 micrometer/1.5 micrometer = 100X <--...
  2. S

    Decay length of the evanescent wave

    Homework Statement A beam of light of vacuum wavelength λ = 550nm passes from water (refractive index 1.33) into air (refractive index 1.00). (a) What is the critical angle? (b) Suppose the beam is totally internally reflected. At what angle of incidence would the decay length of the...
  3. B

    Consistency of Faraday's Law and Electric Field Equation in Optics

    Homework Statement Suppose that an electric field is given by E(r,t)=E0cos(k·r−ωt+φ), where k⊥E0 and φ is a constant phase. Show that B(r,t)=((k×E)/ω)B(k⋅r-ωt+φ) is consistent with ∇×E=-∂B/∂t Homework Equations ∇×E=-∂B/∂t The Attempt at a Solution I know I have to take the curl of E, but I'm...
  4. Jett

    Understanding a Generalization of Snell's Law

    I have been working a project of creating a simulation of thin-film interference in a 3D modeling program, Blender, to be able to create materials that would use its effects. While uncommon, I would love for it to be able to correctly calculate reflectance and transmittance when the incident...
  5. I

    Nonlinear Optics: third-order susceptibility

    Hi. I've just learned about enumerating the second-order susceptibility (rather blindly) by 3^3 * (3*2*1) * 2 = 324. (tensor size * 3 frequency permutation * negative frequency) I'm guessing that for the third-order susceptibility would similarly yeild 3^4 * (4*3*2*1) * 2 = 3888? I couldn't...
  6. Krushnaraj Pandya

    Ray optics conceptual question

    Homework Statement I read that the magnification for a point object is undefined, but when we draw ray diagrams we consider the rays to be emanating from a point source and also define magnification for it- what am I missing? Homework Equations -- The Attempt at a Solution (conceptual query)
  7. Korak Biswas

    A Quantum Optics: Squeezed light generation

    Theoretically, squeezed state can be generated using a process called 'parametric down conversion'. I was going through the literature and found that people performed 'second harmonic generation' before doing 'parametric down conversion'. Can anyone tell me why simple harmonic generation is...
  8. Zubair Ahmad

    Optics question -- Object and Image on the optical axis....

    Is it necessary that the image of the point object placed on the axis of optical system has its image formed on the axis? Consider paraxial approximation.
  9. Erickly

    Film Thickness for Minimum Reflection of Monochromatic Light: How to Calculate?

    Homework Statement Monochromatic light of wavelength, λ is traveling in air. The light then strikes a thin film having an index of refraction n1 that is coating a material having an index of refraction n2. If n2 is larger than n1, what minimum film thickness will result in minimum reflection of...
  10. V

    Courses Are these two optics courses too similar to justify taking?

    There are two courses at my school involving optics. I'm not sure if they are too similar that taking both would be a waste of time, or if they would be different enough that it would be ok to take both. The first one is from the electrical engineering department, here is the course...
  11. K

    Optical Spherical glass vs parabolic acrylic

    Hello, I am trying to buy the parts to perform a Schlieren experiment (see an example here: https://bit.ly/2mwbzkl) It is suggested to use a Spherical Primary Telescope Mirror (glass), however when i look into getting larger than 160 mm versions, they start to get extremely expensive. So...
  12. SJay16

    Courses Theoretical Physics or Optics?

    I was just wondering which out of the 2 courses would be more beneficial for me as I am interested in Astronomy, Astrophysics, and Cosmology: A senior level course in Optics or a Senior Level course in Methods of Theoretical Physics (Presumably mathematical methods). Course Descriptions...
  13. J

    Materials that allow IR or UV light to pass through?

    Glass allows visible light to pass through I would like to find a list of materials that allows lights of different EM spectrum to pass through, not just the above, Searched throughout google, couldn't find any!.
  14. Ravik Rocha

    Difference between real and virtual objects? (optics)

    I do know the difference between real and virtual images. I would like to know the difference between real and virtual objects. I need some examples. See this picture
  15. Lukejohn

    How to state the laws of refraction and apply them to....

    How do i apply the laws of refraction to plane and curved surfaces. I have absolutely no idea how to even start on this one, its got nothing to do with the course, i am going to study. i need to understand this to move on but i genuinely have absolutely no interest in optics. I really can not...
  16. spareine

    Why is the refractive index for red lower than for blue?

    By observing that red is the outermost color of the rainbow it is possible to conclude the refractive index of water, n, is lower for red than for blue. However, why is n lower for red? This seems to be answered by the Drude dispersion model, with a resonance in the ultraviolet region, but I...
  17. SchroedingersLion

    Nonlinear Optics - Pockels effect

    Greetings, is anyone here familiar with nonlinear optics? I want to know wether the Pockels effect only occurs in optically anisotropic media or not. Of course, we need a medium with inversion symmetry ("non-centrosymmetric medium"), but I am not sure about the optical isotropy. In an...
  18. A

    Is there a limit to how steep the refractive index gradient can be

    Is there a limit to how steep a refractive index gradient can be before ray optics are no longer able to predict the path of the light? How is it related to wavelength? Under what conditions the light will be able to travel perpendicular to the gradient In a straight line? (having diffrent index...
  19. Ajaroy

    What is the internal radius of the optical fibre

    Homework Statement A Capillary tube is made of glass of refractive index n1 . The outer radius of the tube is R.The tube is filled with a liquid of refractive index n2 < n1 .what should be the minimum internal radius of the tube so that any ray that hits the tube would enter the liquid...
  20. J

    Optics: Image formed from a glass block

    Homework Statement Homework EquationsThe Attempt at a Solution I have solved this problem . For that I had to use refraction at the first surface , then reflection from the back side and then again refraction from the first surface . This gives me the correct answer . But when I saw the...
  21. HappyBlue

    Mirror: refractive index and thickness

    Homework Statement Hello everyone ! I hope this is the correct place to ask. Here is my probem: I have to measure the refractive index and the thickness of the glass part of a mirror. The idea that I have, and that has been approved by my teachers, is the following: In order to measure the...
  22. M

    Image Formation in Galilei Binoculars: Solving for the Image Position

    Homework Statement A galileibinocular consists of two lenses with ƒobjective = +30 cm and ƒokular = -10 cm. The distance between the lenses is 30 cm and the binocular is aimed at an object 90 cm away from the objective lens. Where is the image of the object seen through the binoculars? (the...
  23. J

    What is the speed of the 5th image in optics with multiple mirrors?

    Homework Statement Homework EquationsThe Attempt at a Solution I have placed the origin at the middle of the mirrors . This means object is at the origin . Now I am bit unsure about what the question means with 5th reflection .I am assuming that it means 5th image in either of the mirrors...
  24. P

    Unpolarised light: Orientation of the E-field

    Homework Statement How does this picture represent a unpolarised light?Homework EquationsThe Attempt at a Solution [/B] I thought light waves were perpendicular to the direction of propogation so if it has diagonal components then isn't that not perpendicular to the wave direction If it is...
  25. M

    Diffraction Grating - Calculating Ruling Width

    Homework Statement The Attempt at a Solution Hi All! This is probably going to have a very simple answer. I'm stuck on question (b)(ii). The only equation I can find with the ruling width in it is the one shown and I can't find a way to calculate is as I don't know Beta. Thanks
  26. harambe

    I How Do Metals Reflect Light Across Different Frequencies?

    https://eng.libretexts.org/Core/Materials_Science/Optical_Properties/Metallic_Reflection According to this article,metals are good reflectors at low frequencies.What about at high frequencies like visible or UV spectrum?Will this show deviation
  27. M

    Imaging optics and lowest possible angle video projection?

    I have a very very unusual project requirement where I need a pocket video projection with the lowest possible projection angle or "longest possible throw-ratio". It's a pocket DLP projector so goal is to have the beam remain ,as much as possible, almost the same size as the DLP matrix, for a...
  28. MattIverson

    Electromagnetic Radiation of Single frequency Incident on a Slab

    Homework Statement The problem is state in the attachment. Homework Equations None to add. 3. The Attempt at a Solution Struggling with this problem because of the phasor part of it. Perhaps this is justified because the angle is very small and so that relates to a low frequency? Is it...
  29. Hydrous Caperilla

    Number of Images Formed from Reflection & Refraction

    Homework Statement [/B] A glass slab of refractive index n=2 has left spherical of radius 10cm and right surface plane.From both surfaces refraction as well as reflection takes place.A point of object P is placed at a distance 15cm from point O1. Mark the correct option (A)two images are...
  30. physics loverq

    B What is the underlying reason for stimulated emission?

    I learned that stimulated absorption, spontaneous emission and stimulated emission are three fundamental concepts in the process of radiation. Among these three concepts, I found stimulated emission really hard to comprehend, it says when atom in its excited state is stimulated by external...
  31. DylanXO

    Contact Lenses Optics Problem (Two-Parts)

    I believe I have answered the first question correctly (although I am not certain of this). And I'm struggling with grasping how to approach the second part of the question. Any guidance or recommedations on reading material would be greatly appreciated. Homework Statement Contact lenses are...
  32. M

    Physics Lens Problem: Find Object Distance

    Homework Statement An object and its lens-produced real image are 2.4 m apart. Part A If the lens has 55-cm focal length, what are the possible values for the object distance? Express your answer using two significant figures. Homework Equations 1/s+1/s'=1/f s-s'=2.4m The Attempt at a...
  33. T

    Photons in Fiber Optics V Solar Sails

    Solar sails use the push of photons on a mirror. Would it work to use the push of photons in the atoms in fiber optic cables so the question is would there be push and how much on 1 mile of a space train 50 feet wide with 1 foot thick of fiber optics. Here's how I think it would be nearly...
  34. W

    I Changing the focal plane of a video projection?

    A bit of unsual scenario, I need to divide a video projection beam horizontally into two. Since the splitted beams in my diagram are treated as a separate beam they have to have their focus plane changed. Is that possible to do and how would one do it? http://image.ibb.co/jAu9x7/9241421.jpg If...
  35. Shadow89

    I In a rifle scope, why is the reticle at the focal point?

    In order for a conventional telescopic riflescope to function, it must invert the image two times. As a result, the light-rays traveling through the tube must meet at two focal points. With my limited knowledge of optics, i assume that parallell light going in through the objective will meet...
  36. Shadow89

    Collimated light from red dot scopes?

    I am trying to piece together how the parabolic mirror manages to reflect the "red dot" from the focal point to the eye without distortion. I compare this with a conventional car headlight, which operates almost exactly the same way, except it has a non-transparent backing. Why does the ret dot...
  37. Altagyam

    Help with optics problem involving diopters

    Homework Statement A nearsighted man uses his ideally prescribed contact lenses that have a refractive power of −3.60 diopters. He would like a prescription for eyeglasses. What is the correct eyeglasses prescription if he wears his eyeglasses a distance of 2.30 cm from his eyes? Homework...
  38. V

    A vessel with fluids of two different refractive indices

    Homework Statement both filled to height h in the vessel of length 2h. one has refractive index root 2 and the bottom fluid has refractive index n. find the apparent depth of vessel. Homework Equations n = real depth/apparent depth The Attempt at a Solution what these guys have done ...
  39. TheSodesa

    The focal length of a microscope eyepiece

    The question: -------------------- The length of a microscope pipe is $L=160\,\rm mm$, the transverse magnification of its objective $M_o = 40\times$ and the diameter $d_o = 5\,\rm mm$. As for the ocular/eyepiece, its magnification is $M_e = 10\times$. 1. Find out the focal length of the...
  40. Arman777

    Optics: deriving Nodal and Principal Points for a thick lens

    Homework Statement I have to derive the Nodal and Principle points distance equations. Homework Equations Equations can be found here http://scienceworld.wolfram.com/physics/ThickLensFormula.html The Attempt at a Solution I have no clue about how to approach this problem. If...
  41. K

    Is the Ideal Lens Calculation Patentable?

    I have patent pending on this. I am publishing despite that. Patents last 20 years at the most, plus it can be researched already. I choose a focal point. I dirve rays from it in a fan fashion toward lens, which for now is in shape of mere segment. The segment has its position in horizontal...
  42. B

    Relationship between interference and arm length in MZI

    A question about the Mach-Zehnder interferometer. My understanding is: If its two arms are equally long, there is destructive interference in one output and constructive interference in the other output. So, the intensity of light detected at the first output should be 0% and at the second...
  43. lbwet

    Calculate Height of Light Pole from Shadow Length

    Homework Statement At the outside, there is a vertical stick with a length of 1.1 meter and its shadow on the surface of an Earth is 1.3 meter, there also is light pole and its shadow length is 5.2 meters, what is the height of that light pole? Homework Equations Trigonometry equations to...
  44. PumpkinCougar95

    B Young's Double slit experiment with different slit sizes

    What would happen if a youngs double slit experiment is done with different slit sizes? I get the feeling that the intensity might never be zero as the waves might never cancel out completely. Am I right? How should I analyse the Intensity? Would I have to do something like what is done while...
  45. R

    Optics question: I need parallel illumination for a Contact Image Sensor (CIS)

    I am experimenting with a CIS from a document scanner (basically a row of photo sensors). I want to detect the position of an object as it passes the scanner bar. Initially in one dimension - x along the CIS. If the object is always a set distance from the light bar, I can provide illumination...
  46. C

    Condition for circular-wire polarizer to transmit no light

    I want to make a wire grid surface that transmits no light. For that I wanted to use quarter-circular arc wires. My question is what dimensions would I need to apply to the wires, would an arc with radius = wavelength of incident light be sufficient (since then it is the size of a wavelength in...
  47. Phil123

    [LENS] Given focal length and height, find object distance

    Homework Statement An object is in front of a convex mirror. We then obtain an erect image whose height is equal to 25% of the height of the object. What is the distance between the object and the mirror if we know that the focal distance is equal to 0.2m? Homework Equations M = Yi/Yo = q/p...
  48. C

    Where do antireflective coatings reflect light?

    Lets consider an index matching antireflective coating on a conducting substrate (i.e. salisbury screen). The waves reflected destructively interfere in the direction of specular reflection. However, the energy has to be conserved, and since it is not transmitted, it most me reflected in a...
  49. T

    Wave Physics - Optics - Effective Focal Length

    So we have the focal lengths: f1, f2, ..., f7 = 25mm And the distance between the lenses: d1-2, d2-3, ..., d6-7 = 50mm I have figured out that if the system would be afocal if it had an even number of these lenses. This is because the focal length of two adjacent lenses is the same as the...
  50. C

    Does a Single Metal Stripe Reflect Polarized Light at the Angle of Incidence?

    I know that only light with polarization in the plane of the "stripe" gets reflected. What i need to know is if a single metal stripe could reflect such polarised light at ONLY the angle equal to the angle of incidence or do only a whole array of stripes produce specular reflections? Sources...
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