Refraction Definition and 89 Discussions

In physics, refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.
For light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence θ1 and angle of refraction θ2 is equal to the ratio of phase velocities (v1 / v2) in the two media, or equivalently, to the indices of refraction (n2 / n1) of the two media.

















{\displaystyle {\frac {\sin \theta _{1}}{\sin \theta _{2}}}={\frac {v_{1}}{v_{2}}}={\frac {n_{2}}{n_{1}}}}

Optical prisms and lenses use refraction to redirect light, as does the human eye. The refractive index of materials varies with the wavelength of light, and thus the angle of the refraction also varies correspondingly. This is called dispersion and causes prisms and rainbows to divide white light into its constituent spectral colors.

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  1. Remixex

    Estimating the velocity of seismic waves through an idealized Earth

    Hello, this is a repost from a much less-clear question I posted before (link to question: It's kind of a loaded question, however it can be expressed as triangles...
  2. Remixex

    Triangles inside a circle to represent raypaths inside an ideal Earth

    I have managed to get some of the required distances and angles. I have the distance ##a##, the velocity inside the mantle, the total radius of the Earth ##R_t## as well as mantle and core radii. I have also figured out the angle of incidence, however I cannot get the refracted angle with the...
  3. L

    Position of the image of an object placed in water

    I tried using the formula for the refraction of a spherical lens ##\frac{n_1}{p}+\frac{n_2}{q}=\frac{n_2-n_1}{R}## consider each slab as a spherical lens with curvature ##R=\infty## and by doing that I get ##\frac{1.33}{10}+\frac{1.5}{q}=0\Leftrightarrow q\approx -11.3 cm##. Since the piece of...
  4. L

    Light incident on a sphere, focused at a distance ##2R##

    I used the equation for the refraction on a spherical surface: ##\frac{n_1}{p}+\frac{n_2}{q}=\frac{n_2-n_1}{R}##, where ##n_1=1## is the index of refraction of air, ##n_2## the index of refraction of the sphere, ##R## is the radius of the glass sphere, ##p## is the object distance which, since...
  5. mcas

    Estimate the following quantities from a graph of the refractive index of NaCl

    a) I managed to obtain some results that are roughly around what is given in the answers. Because \varepsilon_{st} and \varepsilon_{\infty} are values of \varepsilon_{1}, I used this approximation: n\approx \frac{1}{\sqrt{2}} (\varepsilon_{1}+\sqrt{\varepsilon_{1}^2})^{1/2} -> \varepsilon_{1} =...
  6. lemma28

    B Fermat's principle and refraction -- Possible misunderstanding

    Consider a light starting at A in media 1 and going in and out a media 2 (say shaped as a disk) with relative index of refraction n to arrive at point B (in media 1). Fermat's principle says that the path taken by the ray between points A and B is the path that can be traversed in the least...
  7. R

    Refraction of light question -- Flintglass submerged in oil

    Hello, hopefully the question made sense, it was hard to translate. i attached a photo about the question. I started with n1=1.4, sinΘ1=37◦ and n2=1.62 1.4(sin(37◦))=1.62sinΘ2 1.4(sin(37◦))/1.62=sinΘ2 arcsin(0.52)=31.34◦ Is it calculated correctly?
  8. H

    Phase lag of light in materials

    There are 5 fantastic videos in this website: He is a very good educator and it is also very good to see those authentic experiments and aparatus. Anyway, in the following one at exacly 8:00 minutes he says that the phase lag induced by the dipole is always 90...
  9. F

    Why does the amount of Refraction depend on wavelength?

    I understand that electrons of a material have a natural frequency of vibration and the refractive index results from the phase difference between the incident light's field oscillations and the field oscillations of these electrons...
  10. K

    Size of a fish under water

    From This picture, I think the fish will be smaller but the problem is how small will it be? (Fish "L" is the image of fish "K") Let ##H## be the depth of fish "K", ##\theta## be the angle of eyes to y-axis and ##n## is the index of refraction of water.
  11. G

    Internal reflection equation question

    As you can see we have 3 media here. Only focus on the glass and coating medium. Assume an incident ray comes from the air medium and is refracted inside the glass and then it is refracted again in the coating medium. The x angle is the angle inside the glass medium. In this case, if the...
  12. C

    Size of a light beam before and after Refraction

    The size of light beam is same or different before and after refraction from a medium. If same then why we can not prove from mathematical expression. If not same why?
  13. Jaffer2020

    Refraction of light -- What is the best description for 10th grade physics students?

    In my latest 10th grade physics lesson, we were learning about the refraction of light. I decided to share what I knew about why light slows down in a vacuum, which is, in short, because the electric field of the electromagnetic wave exerts a force on the charged electrons of a medium, which in...
  14. K

    Calculate the focal distance of the duplicate

    The picture below shows a so-called chromatic doublet, which is designed to minimize chromatic aberration, ie the wavelength dependence of the refractive index of the glass. The first lens has a flat first surface and a concave second surface with radius of curvature R and index of refraction n1...
  15. K

    Find the refractive index for the lens and find the image distance

    A thin lens has an upper radius of curvature 𝑅1 and a lower radius of curvature 𝑅2. When the lens is completely surrounded by air, it has a focal distance 𝑓. The lens is then placed in the interface between air and water inside a vessel (see figure). Calculate the refractive index for the glass...
  16. M

    Combination lens equation questions

    Homework Statement: Lens questions. Homework Equations: idk Hello, so I was wanting to use a laser beam and purchase a few lens' online for a project and wanted to get something similar to the image below, where i would end with a horizontal light ray i was wondering if anyone knows the...
  17. DPMF6973

    Index of refraction and wavelength

    The problem is multiple choice. A) refraction b) diffraction c) reflection d) dispersion An explanation would also be greatly appreciated!
  18. F

    The maximum intensity for light transmitted through a thin film

    Homework Statement A thin (460 nm) film of kerosene (n=1,20) is spread out on water (n = 1,30). Light hits the (horizontal) surface of the film coming (almost) perpendicularly from above. A diver underwater, below the film. a) Find out the visible wavelength reflected into air that has the...
  19. 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.
  20. The proof of Snell’s law using springs - 3blue1brown

    The proof of Snell’s law using springs - 3blue1brown

    The law of light bending in matter. Also an important law for the proof of brachistochrone problem.
  21. S

    Dolphin Underwater Problem

    Homework Statement A scientist investigating the movements of dolphins in the Mediterranean uses a dart gun to shoot small, harmless tracking devices onto the fins of dolphins. When standing on deck, her hand is 1m above the water, and looking along the dart gun she is holding at an angle of...
  22. M

    The refractive index of an unknown liquid

    1. A light ray in dense flint glass that has an index of refraction of 1.655 is incident to the glass surface. An UNKNOWN liquid condenses on the glass's surface. Total internal reflection on the glass-liquid interface occurs for a minimum angle of incidence on the glass-liquid interface at...
  23. 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...
  24. 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?
  25. K

    Atmospheric Refraction

    Does atmospheric refraction only work at certain temperatures, distances, and shape of the object (i.e. only spheres)?
  26. 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...
  27. Nabin kalauni

    B What does coefficient of increase of physical quantity mean?

    I am extremely confused by the use of the term coefficient of increase of something. For example , if it is stated that the index of refraction varies linearly with a coefficient of 2.5×10^-5, how is this coefficient defined? Is it simply the slope of the line plotted with index of refraction on...
  28. harambe

    Bird-Fish refraction

    Homework Statement A vessel is filled with water of refractive index 4/3.The height of the vessel is 60cm.A fish F is at 40 cm below the surface of water.A bird B is 30cm above the surface of water.The bottom of the vessel behaves as plane mirror. How many images of fish will be seen by the...
  29. Muhammad Danish

    Reflection and Refraction formula help

    Homework Statement 2. Homework Equations 3. The Attempt at a Solution [/B] I tried to solve this question with the general formula n=sin i / sin r. 1.5 = sin 30/sin r, r = 19.4 = 19 which is option A. But option A is incorrect. Please guide me where am I wrong..
  30. T

    Non Newtonian / Newtonian Fluid interface

    Suppose I have a wave tank partially filled with a shear thickening Newtonian fluid (Oobleck), on top of which sits a layer of water (separated by a thin membrane to prevent mixing) If I propagate a surface wave in the water layer how will it conduct itself at the Newtonian/Non Newtonian Fluid...
  31. D

    Bend in a fiber optic cable

    If there is a fiber optic cable with a diameter d, the index of refraction of the cladding the cable is given, and so is the index of refraction core of the cable, how would you formulate an equation for the minimum radius of bend the cable can have? Thank you in advance.
  32. K

    Does light refraction play a role in bubble iridescence?

    We know interference of waves play a role in causing "colors" on soap bubbles. But does light refraction play a role in bubble iridescence? When the light wave travels into the soap bubble surface, won't it refract since the wave is into a different matter (what matter the soap bubble surface...
  33. D

    I What properties allow me to see past Earth's curvature?

    I recently was able to view a 193 foot building from 24 miles away. The base of the building is approximately 15 feet above sea level and my eye level was approximately 9 feet above sea level. I was viewing the building across a Lake. I could see a substantial amount of the building, which...
  34. M

    Effect of electrical permittivity on the speed of light?

    Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level? I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...
  35. R

    Refractive index as a function of the concentration of a sugar solution

    We recently performed an experiment with the idea to find refractive index of medium (water) as a function of wavelength of light. We then added some sugar to see how the refractive index changes with concentration of sugar solution. We got the following graphs. Are the relationships...
  36. G

    I Overview of General Fresnel Equations + Complex IORs

    Hi, My understanding is that when light (with some frequency and polarization) hits the interface between two media (each with some frequency-dependent material properties), the Fresnel equations apply. This tells us how much light reflects back versus refracts across the interface. I'm...
  37. Z

    Using Snell's Law for Brachistochrone Project

    Hi all, I'm after a little guidance for I do not know what is going wrong. I understand that for Johann Bernoulli's proof of the brachistochrone problem he used refraction of light and Fermat's principle of least time. I have decided to do a project on the subject, in which I am dividing up a...
  38. Const@ntine

    Refraction in Cylinder.

    Homework Statement A non-transclucent container in the form of a cylinder, has a diameter of 3.00 m, has its top part open, and is filled with water. When the sun created a 28.0 degree angle with the horizontal, the light doesn't illuminate the bottom of the container. What's the depth of the...
  39. C

    I Minimum deviation in prism spectroscope

    Suppose that I use a prism (vertex angle ##\alpha##) spectroscope to analyze a beam of visible light from a mercury lamp (different wavelenghts) and I want the determine the refraction index of the prism using the minmum deviation angles ##D_{min}##...
  40. Biniamin Piash

    Sweat on Screen, Interference or Refraction?

    When we touch the screen of a mobile or laptop we can see some colors on the sweat adhered to the screen.Which property of light can explain it? Is it for interference or for refraction?
  41. J

    Coating Eyeglass Lenses(destructive interference)

    Homework Statement Eyeglass lenses can be coated on the inner surfaces to reduce the reflection of stray light to the eye. If the lenses are medium flint glass of refractive index 1.62 and the coating is fluorite of refractive index 1.432, (a) what minimum thickness of film is needed on the...
  42. J

    Conservation of energy in refraction

    Hello, This has been bugging me for some time now, so I would be interested to see what I have been missing so far. Imagine a single ray of light (made up of many photons) hitting a perfectly non-absorbing (for this wavelength of light) spherical dielectric object, which has finite mass. The...
  43. baba bakjohikoplop

    How would a person under water see sunset and sunrise?

    A person completely under sea water tracks the sun. Compared to an observer above water, which of the following observation would be made by the underwater observer? Neither the time of sunrise or sunset nor the angular span of the horizon changes sunrise is delayed, sunset is advanced but...
  44. S

    Optics Question: Prisms

    Homework Statement The two rays shown below, a and b, have different wavelengths. They travel through the glass prism as shown; 1) is this possible? 2) If this is possible, which has the longer wavelength, ray a or ray b? [see attached figure] Homework Equations λ = λi/n critical angle =...
  45. S

    Applying Snell's Law Inside & Outside a Prism

    Homework Statement I'm having trouble / uncertainties about the third missing angle (from left to right) in the picture. The first angle of reflection was easy as it's just 34 degrees aswell and I used snell's law rearranged to find the first angle of refraction as 13.36 degrees from the...
  46. Cocoleia

    Equation for the boundary of rays turning to plane waves

    Homework Statement I am given the following figure: These are converging rays that appear to be going to a point F convert to a plane wave upon hitting the boundary between n2 and n1, and I am asked to find the equation for the boundary between n1 and n2 that perfectly accomplishes this...
  47. F

    Does the apparent length of an object change in water?

    Here is a problem that showed up on my exam that I couldn't find any variation online. A stick of length L is depth D in the water. The stick is parallel to the surface of the water, and the viewer (in air) is looking down in the water right over the middle of the stick. What is the apparent...
  48. L

    B What is this tool named?

    Hi! I'm doing a light research project and to have a refraction and reflection ( I don't know if it's like this in eglish) visual representation I came up with this photo. I don't know the name of this tool and also what is it made of? In my opinion is just a glass but I dont really know. Thanks!
  49. Cocoleia

    When can internal reflection be used to find the index of refraction

    Homework Statement I need to describe an experiment in which I would use internal reflection to determine the index of refraction of material Homework Equations Snell's law The Attempt at a Solution I understand the concept of internal reflection, such as the critical angle etc. I am just...
  50. F

    Intuitive reasoning for frequency remaining constant during refraction

    What is the intuition for why the frequency of light does not change as it passes from a less dense medium to a denser one (or vice versa)? Classically, if we treat light in terms of waves, then intuitively, is the reason why the frequency does not change because it is determined by the...