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. Andy1011

    Nonreflective Film: Solving the Ref. Index Problem

    I thought of sandwiching the coating between lens sufaces and then applied the condition of minimum which gave a thickness of lambda/2*ref. Index and I got totally stuck at the ref. Index.
  2. L

    Image position and magnification for underwater spherical lens

    Using the data given and recalling that in this configuration ##R<0## I get: ##\frac{1.33}{0.5}+\frac{1.5}{q}=\frac{1.5-1.33}{-0.2}\Rightarrow q\approx -0.427 m=-42.7 cm## so the image is virtual and is ##42.7\ cm## to the left of vertex ##V##. The magnification is ##M=\frac{n_1 q}{n_2...
  3. N

    I Lens angle of coverage/image circle

    Hello, I was wondering what parameters determine the angle of coverage/size of the image circle of a lens. For example, for a fixed focal length, aperture and flange focal distance of a camera, what can a lens designer do to change the size of the image circle. I'd also like to know how the...
  4. jerry222

    Interference of light in thin films

    Phase difference is $\phi=\frac{2pi}{\lambda}* \Delta+\pi$ Phase difference, max: $\Delta \phi=2pim=\frac{2pi}{\lamda_{max}}*2nd$ Phase difference, max: $\Delta \phi=2pim=\frac{2pi}{\lamda_{min}}*2nd+pi$ Flim thickness: $d=100nm$ Set the equations equal to each other i got a d=-100nm which...
  5. A

    Procedure to express radiation intensity of an LED in watts/cm^2

    I am calculating Responsivity of a pn junction photodiode (a.k.a the target) by irradiating radiation from LED sources. For this purpose, i have two LEDs, one UV and another green LED. Note that LEDs are placed close to the target.UV LED : Manufacturer has given total radiant power to be 20mW...
  6. ynyin

    I Rotating Polarization with Optics: Exploring the Principle

    In optics experiments, I often see the following optics configuration to rotate the polarization of an incident linearly-polarized laser beam. The final reflected beam has its polarization rotated by 90 degrees. My question is: 1) Between the quarter plate and the mirror( reflecting surface)...
  7. E

    Engineering Photonics / Fibre Optics - (Supermodes, PBGFs, Coupling)

    Hi, Looking for a good photonics / fibre optics textbook that covers the field, while also addressing said topics in the title. Thank you!
  8. rishurboi

    I Applications of Virtual objects

    I've heard virtual objects are used in cinema halls I'm not sure of what that means, can someone explain this to me please? And btw by virtual object i mean when diverging rays from real object passes through a convex lens, the rays will converging and if you'll place a plane mirror infront of...
  9. tomceka

    Geometrical optics: using Snell's law, find the depth of the pool

    α=30°; l=0.5 m; n1=1; n2=1.33 α+β=90°, so β=90°-30°=60°. Using Snell's law: sinβ/sinγ = n2/n1 sinγ≈0.651 γ≈41°. β=γ+θ (vertical angles) θ=60°-41°=19° tan(θ+β)=l/h h=l/tan(θ+γ) h=0.5/(tan(19+41))≈0.289 m
  10. F

    Finding Total Number of Optical Field Modes for Visible Light

    ρ_kdk = k^2/π^2 dk is the density of field modes (what we are trying to solve for here), and as ρ_kdk = ρ_λdλ, and k=2π/λ, we can rearrange this to get ρ_λdλ = 8π/λ^4dλ This is where my confusion lies. I am not sure what to do next. I know this equation physically means the number of modes per...
  11. L

    A problem involving thin film interference

    I know that every time that light goes from traveling through a medium with lower refractive index to one with a higher refractive index the reflected light undergoes a ##\frac{\lambda}{2}## phase change. Since this happens both at the air-plate and plate-glass interfaces we have that the phase...
  12. samy4408

    I What does "upright" mean in geometric optics?

    if someone want to explain to me what is an upright image ? , and what are the other adjectives to define an image in geometric optics and their meaning , Thanks .
  13. A

    Exploring the Intersection of Chemical Engineering and Optics: A Ph.D. Journey

    I am doing a Ph.D. in optics in the UK. Nonetheless, my core formation is as a chemical engineer. That is why I lack some knowledge about optics that I am actively going to look for answers and figure out my unknowns in this forum.
  14. Father_Ing

    Two concave mirrors on a table

    I'm currently confused in determining whether an image formed by the 1st mirror (the left one) is a real or virtual object for the 2nd mirror. Here is the solution manual: This is what I have in my mind: Since the object is located between the focus and radius point of the first mirror, the...
  15. EBINESH

    I Help Needed for Lens Selection for Fiber optics

    I am using a fiber optic cable through which led light propogate, fiber's half acceptance agle is 30 degree. I want to make the light (diverging)comes out of fiber into collimated beam and this collimated beam will pass through filters, sample and will be used for Fluoroscence application. hope...
  16. C

    A Absorption and emission spectrum in quantum optics

    The emission spectrum or resonance fluorescence for a quantum dot, atom or defect center are discussed in many quantum optics textbook, for example see "Quantum Optics" by Marlan O. Scully and M. Suhail Zubairy Chapter 10 , "Quantum Optics" by D. F. Walls and Gerard J. Milburn Chapter 10 and...
  17. B

    Correct Angle for FSW in Fabry-Perot Interferometer

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  18. yglo98

    Optics. A laser beam is refracted in a piece of glass.

    A red laser with the diameter of 3mm is directed towards a piece of glass. It has the effect, P of 1mW. The angle of incidence is 90 degrees. The glass has refraction index n2= 1,5 and thickness 2 cm. Its front side is convex with a convergence radius,R, of 11 cm. The back side is plane. Whats...
  19. warhammer

    Intensity Distribution of Superposition of 2 Waves

    We assume incident waves to be: y(1)=y(o)sin(wt) y(2)=3y(o)sin(wt+Φ) As Intensity~(Amplitude)^2 We get y(2)=3y(1) This gives us I(2)=9I(1) We assume I(1)=I(o) & I(2)=9I(o) Resultant Wave Intensity I=I(1)+I(2) +2√(I(1)*I(2))*cosΦ ----> I(o) + 9I(o) + 6I(o)cosΦ (We can take cos of this...
  20. T

    A Reflectivity with gradient in refractive index

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  21. warhammer

    I On 'A Quarter Waveplate (QWP) rotated between 2 Polarisers'

    While going through the book 'Problems & Solutions in Optics and Photonics' I was having difficulty in understanding a question & have some issues about my own conceptual know-how in this regard. The Question is: A quarter-wave plate is rotated between two crossed polaroids. If an unpolarised...
  22. theycallmevirgo

    Simple(?) parabolic dish design question

    I want to use this to design a parabolic (optical) mirror; The problem is that in my application I need both D and f to be a parameter, but I need to specify f only as a perpendicular distance from D. In other words, I need to specify some f_2=f-d, and calculate d. I can't seem to come up with...
  23. warhammer

    Question on Resolving Power of Diffraction Grating

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  24. L

    Medical Regeneration of optics nerves -- How?

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  25. fluidistic

    I How to "think" of a polarizer in matrix representation?

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  26. warhammer

    I Correct Formula for "No Fringe Condition" (Michelson Interferometer)

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  27. J

    I Using Diffraction (i.e., Fresnel Zone Plate) to defocus/diverge light

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  28. rinalai

    [Optics] Questions on the Stokes shift

    Here is my answer to this question: Stokes shift is the difference in wavelength between positions of the band maxima of the excitation and emission spectra of the same electronic transition. When Stokes shift is large, it means there is more energy loss, which is not favorable regarding...
  29. rinalai

    [Optics] Compound microscope (homework quiz)

    R = 1.22*700nm/(1.3+0.95) ≈ 380nm
  30. yucheng

    Astronomy Technical, physical text on (astro)photography & telescopes?

    It appears that many texts on astrophotography and telescopes for amateurs tend to avoid mathematical formulas, as such, they are of little use to do some practical calculations. What I am interested in is: Magnification Image scale Focal length Focal plane and sensor plane! (CCDs!) Focal-ratio...
  31. G

    How do dark spot and tiny hole filters affect Fourier optics images?

    I was assigned an experiment of Fouriers optics where I have to use different Filters. One of them was the dark spot and the tiny hole. As of my understanding, for tiny hole, we cut off all high-frequency light related to diffraction and refraction, thus using only the low freuency part of the...
  32. J

    A How to calculate the temperature change of a laser-irradiated material

    I am looking to approximately calculate the temperature change of a sample that was exposed to a laser pulse. Experimentally, we know the optical absorption, reflection, and transmission, as well as the source parameters for our laser system. I realize that I will have to make approximations...
  33. Marioweee

    What is the focal point of a lens in a geometrical optics problem?

    I have recently started with geometric optics and I do not quite understand what this problem asks of me. According to the statement, the focal point of the lens would be -25.5cm, right? That is, it is only a problem of concepts where it is not necessary to take into account the radii of the...
  34. V

    Best layman non mathematical interesting book on Ray and wave optics

    A book on optics which is less mathematical maybe a similar one to physics for poets or gamow gravity classics
  35. Yukatto

    Engineering Recommended book for Optical Engineering graduate

    I am a recent Optical Engineering graduate, It's easy to forget about concepts that I learned, so I would like to have a book to that can help me while preparing for job interviews, a book to help me remember the most important concept in Optics and Optical Engineering. Can anybody recommend...
  36. Ebi Rogha

    I Can a single photon be reflected by a mirror?

    If the answer is Yes, then I would ask, if the mirror absorbs a portion of the energy of the photon, so the photon should simply stop existing because we cannot have a smaller package of light than a photon. If the answer is No, then I would ask why a beam of light (which is made of a big...
  37. B

    Solid angle in an optics problem (artificial irradiance of the Earth)

    The actual problem can be found as #2 on this link: https://ocw.mit.edu/courses/mechanical-engineering/2-71-optics-spring-2009/assignments/MIT2_71S09_ups1.pdf I rewrote the problem above with the solar irradiance data that they give. My interpretation is of a square 1 m x 1 m plane sitting...
  38. B

    Show that Faraday's Law holds

    I've calculated the negative time derivative of B(r, t) as: $$-\frac{\partial B}{\partial t} = k~\text x~E_0~\text{sin}(k \cdot r - \omega t + \phi)$$ The cross product can be easily expanded, I'd just rather not do the LaTeX for if I can avoid it. The Curl of the electric field...
  39. B

    Multivariable Calculus proof for Optics

    Part A) For part A I forgo breaking down the identity into it's component x, y, and z parts, and just take the r derivative treating r' as a constant vector. This seems to give the right answer, but to be entirely honest I'm not sure how I'd go about doing this component by component. I figure...
  40. stephen8686

    Courses Quantum Optics, Feeling Overwhelmed and Underprepared

    I am an undergraduate at a fairly well known research university. I have taken undergraduate QM 1, QM 2, and the graduate course on Quantum Optics. I got As in all of them and found them not very difficult. Now I am in a research group researching superradiance. I do not feel like any of my...
  41. O

    Other Photovoltaics-Condensed Matter or Optics?

    Hi guys, I'm a rising Junior in physics. I would really like to pursue an applied physics PhD program to study photovoltaics, likely something to do with nano-photonics. My problem now is that I'm a research assistant in a condensed matter experiment lab, focusing heavily on spectroscopy. Will...
  42. I

    Interferometric autocorrelation of sech^2 pulse?

    I know that from intensity autocorrelation, I simply need to divide the FWHM by 1.53 for sech2 pulses. But I can't seem to be able to find any reference on how to get pulse width from interferometric autocorrelation signal. Can someone help me?
  43. O

    What Formula Do I Need for This Optics Problem?

    Unfortunately, there's no formula i know about, so i have no idea how to solve this... Hope you can help me out... Greetings
  44. B

    In optics what do Tp and Ts stand for and what are they?

    In optics what do Tp and Ts stand for and what are they? I believe Tp is the highest amount of light transmitted and Ts is the Lowest amount of light transmitted though a material. but I cannot find that much information on these terms.
  45. G

    Optics question: Looking at mirrors from parallel to the surface

    I did a little experiment recently where I took a plane mirror and held it underneath a ceiling light. Then, I began to lower my head so that my view was closer and closer to the surface. When I did this, the image of the light began to drift lower and lower in the mirror until it completely...
  46. T

    Mysteries of Geometric Optics In MTW Chapter 22

    At the start of this section §22.5 (Geometric Optics in curved Spacetime), the amplitude of the vector potential is given as: A = ##\mathfrak R\{Amplitude \ X \ e^{i\theta}\} ## The Amplitude is then re=expressed a "two-length-scale" expansion (fine!) but it then is modified further to...
  47. D

    Cauchy's law from Lorentz model

    Hello fellow physicists, I need to prove that when ##\omega << \omega_0##, Lorentz equation for refractive indexes: ##n^2(\omega) = 1 + \frac {\omega^2_p} {\omega^2_0 - \omega^2}## turns into Cauchy's empirical law: ##n(\lambda)=A+\frac B {\lambda^2}## I also need to express A and B as a...
  48. B

    Optics Equations - to reduce height

    Is there an optics equation that can take an existing optics set-up and tell you would components, you would need to reduce the distance and still get the same result? I have a working system, but it is really larger and I would like to reduce the distance, the height. I am using a light source...
  49. alya

    Help Needed: Deriving Formula for Computer Undergrad's Final Project

    My mentor wants the derivation of this formula. Me a computer undergrad, unable to figure it out, and my final project are on a halt due to this, any help from the community is greatly appreciated!
  50. D

    Refractive index less than one

    Hello fellow users, I've been given the Lorentz model to calculate the refraction index of a dielectric, the formula in its simplest way states that: ##n^2(\omega) = 1 + \frac {\omega^2_p} {\omega^2_0 - \omega^2}## Where ##\omega_p## is the plasma frequency and ##\omega_0## is the resonance...
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