What is Reflection: Definition and 953 Discussions

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection.
In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors.

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  1. N

    Reflection and Transmission of acoustic waves at a boundary

    Homework Statement An interface is formed between a block of aluminium (density = ##2.70 \times 10^3 kg/m^3##, speed of sound =##6.40 \times 10^3m/s##) and a block of copper (density = ##8.96 \times 10^3 kg/m^3##, speed of sound =##4.76 \times 10^3m/s##). Longitudinal waves traveling through...
  2. S

    Mystery of Reflected Sunlight 73 Miles Away - A Man's Quest

    I read in a book about a man who saw the sun reflected off a distant object on a mountain some 73 miles away in clear visibility. He saw this on many occasions and always wondered what it could be. He states that he asked two of his friends who were going that way if they would check it out...
  3. D

    I Trigonometry problem for collision detection and reflection

    A particle moves from point 0 to point 2. Both positions are known. The center of the circle and it's radius is also known. I am trying to work out the position of 1 where the particle strikes the circle. This is for a 2D astronomy simulator to work out where a particle will strike a 2D...
  4. M

    MHB How do I sketch the reflection of line segment AB about the line y = x?

    The endpoints of line AB are given to be (-1, -2) and (-5, -2). Sketch the reflection of line segment AB about the line y = x. As I understand this concept, I must show that the line y = x is the perpendicular bisector of the line segment AB. Two points are given. This tells me to find the...
  5. M

    Shining light on a retreating object

    Homework Statement I came up with this thought experiment last night, but I'm not confident in my solution--mostly because I forgo the time values I thought would be necessary to complete it. A reflective object moves past a lamp at time T0 with constant (non-relativistic) velocity V...
  6. P

    I Reflection of a massive particle

    Is the reflection of a (massive) quantum particle from a mirrored surface considered a Lorentz Boost?? If it is non-collinear ?
  7. E

    Dielectric slab and angle of incidence

    Hello! Let's consider a plane wave represented by a ray, propagating in a 2D dielectric slab. It has a medium with refractive index n_1 as its core and a medium with refractive index n_2, n_2 < n_1, as its cladding. In order for this ray to represent a mode, it must satisfy two conditions: -...
  8. W

    What is the amplitude of the electric field (laser reflection)

    Problem we are looking at :A laser beam has diameter 1.30 mm . The beam exerts a force of 3.7×10−9 N on a totally reflecting surface. What is the amplitude of the electric field of the electromagnetic radiation in this beam? (Emax) Relevant Formulas...etc.: I have the formula...
  9. C

    I Visible light reflection v.s X-Ray reflection

    I'm a bit new to studying physics so I hope this question doesn't sound off. I already know this "Photons are emitted from an atom when an electron transitions from one state to a lower-energy state. The energy of the emitted photon equal to the difference in energy between the two states."...
  10. Cocoleia

    Thin film appears red, thickness of this part?

    Homework Statement A thin film of oil (n=1.5) is floating on top of water. When looking directly at this film, a large portion appears red (700nm). What is the thickness of the red part of the layer? Homework EquationsThe Attempt at a Solution Since n for oil > n for air, there will be a phase...
  11. Cocoleia

    Thin film interference and external / internal reflection

    Homework Statement I am working on a thin film interference problem where i have to find the phase difference. What is the relationship between external/internal reflection and the thin film interferenceHomework Equations for external: [/B] for internal: The Attempt at a Solution So far i...
  12. SunandaGoh

    Total Internal Reflection / Reflection. What's the answer

    Homework Statement Homework EquationsThe Attempt at a Solution https://scontent-kul1-1.xx.fbcdn.net/v/t35.0-12/15146781_1334186669946177_363846788_o.jpg?oh=b75be99f63eba2e70db5e0287581076b&oe=583538C2 The answer given by the book is " Reflection ". But why isn't it Total Internal Reflection ?
  13. Z

    Snell's law and law of reflection derivation -- confusing

    I am learning principle of optics written by Born&Wolf and confused with the method to derive Snell's laws and law of reflection. In the textbook,##v_1## is the speed of light in mediator 1 and ##v_2## is the one in mediator 2. ##{\vec s}## is the direction of light and ##{\vec r}## is the...
  14. 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 as well and I used snell's law rearranged to find the first angle of refraction as 13.36 degrees from the...
  15. rxrus

    I How see through the glass + reflection at same time

    When its day we can kind of see our reflection a little bit and also see outside, when its night we can fully see our reflection in the glass window. Can someone explain quantum mechanics behind it because i think iv read an article long time ago on it but can't find it anymore.
  16. W

    Can anyone explain this sun reflection in terms of angles?

    I'm trying to understand the physics of reflection to better draw objects. Normally, you see the reflection of a light source on metallic surfaces where the angle of incidence can equal the angle of reflection. This should reflect an image of the source that is approximately equal in size to how...
  17. L

    B What is this tool and how is it used to study light?

    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 don't really know. Thanks!
  18. Clara Chung

    2 Sound waves reflection easy problems

    Homework Statement Refer to the photos, question 21 and 22(the one with a helicopter) Homework Equations Both answers are A The Attempt at a Solution for question 21, if the counts to ten, there are 9 intervals. I divide 20 by 9 and divide it again by 2 and get 1.1s not 0.5s. for question 22...
  19. 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...
  20. A

    Mutilple beam reflection question in Fabry-Perot cavity

    Homework Statement Just having some trouble with a question about Fabry-Perot intereferometers. Here's the question: a) Consider a beam of light undergoing multiple reflections in a Fabry-Perot cavity between two surfaces, both with reflectance R, and with no absorption. Homework Equations...
  21. M

    Derivation of Reflection and Transmission coefficients of wave

    Hi folks, I´m trying to derivate the reflection and transmission factor between solid-solid interface according to prof. Rose´s book "ultrasonic waves in solid media". In this chapter, I´ve found there a few mistakes. however the first two rows in matrix M are correct. Can you please give me...
  22. J

    Fresnel reflection coefficient for Second Harmonic Generation (SHG)

    Hello everyone, this is my first post so I don't know whether or not this is the right thread to be asking this question (if so I am sorry). I am currently working on my thesis where I am determining the thickness of a GaN crystal through second harmonic generation. However in a article...
  23. E

    Why water looks transparent while spray looks white?

    The water looks transparent, but when the water hit the stone, it looks as if it turns white? Why?
  24. RabbitWho

    Virtual image on the perpendicular

    Homework Statement The book ("Real World Physics") says A virtual image in a plane mirror is on the perpendicular from the object to the mirror Homework Equations I know that the normal line is perpendicular to the surface of the mirror And I know that the angle of the incidence and reflection...
  25. Carlos de Meo

    Black bodies, perfect reflection and heat transfer

    Hi Guys While studying physics for my masters (doing it in material science engineering), huge amount of questions appeared. First, let's imagine two experiments 1) One enclosure with perfect reflective walls (R=1 over the entire thermal radiation spectra) at a temperature T1 and a body inside...
  26. Carlos de Meo

    A Why does a higher absorption coefficient result in a smaller emissivity value?

    Hi Guys Im studying some thermal properties for my masters and while reading an article a weird thing happened: As far as i know, a good emitter must be a good absorber (since emission happens "after" absorption") Combining Fresnel equation for a medium that absorbs radiation and Kirchoff law...
  27. Coco Hwang

    Exploring Reflection in a Plane Mirror

    1) If the angle of incidence of a ray of light to mirror is 50 degrees, what is the angle of reflection from the mirror? 2) If the angle of incidence of a ray of light to a mirror is 20 degrees, what angle does the light ray make with the mirror when it reflects? 3) If a ray of light makes an...
  28. S

    Transmission of mechanical wave on two different ropes

    Homework Statement Two infinite ropes, rope 1 and rope 2, of same linear density ##\mu=0.1 kg/m## have the same tension ##T=100N## and lie on the same plane, one perpendicular to the other. The two ropes are connected in the origin. On one of the two branches of rope 1 an harmonic wave is...
  29. V

    Reflection vs absorption and emission

    Greetings, Is there a difference between reflection of radiation and emission after absorption? What causes this difference? Another related question: According to wikipedia: "Earth's surface and the clouds absorb visible and invisible radiation from the sun and re-emit much of the energy as...
  30. D

    FLP: Derivation of reflection coefficient

    In Vol. I Ch.33 of Feynman's Lectures (http://www.feynmanlectures.caltech.edu/I_33.html), 33-6, the reflection coefficient as a function of angle was derived. I am confused about the part where it said the component of A perpendicular to B (Acos (i+r)) has the right polarisation to produce B...
  31. R

    Can light escape the medium when total internal reflection occurs?

    So I just very recentlyearned about total internal reflection, which basically states that when the incident angle is large enough, the light will reflect back into the medium. I have a few questions: Say we have a set up with a tank of water and a laser pointer in it 1) does this mean that if...
  32. jfulky

    Internal Reflection / Fiber Optics

    Homework Statement 3. A fiber optic cable is essentially a thin fiber of plastic with n = 1.46, surrounded by a protective material with n = 1.32. The light can travel around a bend in the fiber if it can internally reflect inside the fiber. If the diameter of the fiber is d = 0.900 mm find the...
  33. spareine

    Do soap bubbles reflect sound?

    Bats in my garden do not seem to notice soap bubbles. Do soap bubbles reflect sound?
  34. bananabandana

    Reflection and Transmission of Plane Waves at a Dielectric-Metal Boundary

    Homework Statement Sorry for the dull question. Problem is as shown/attached Homework Equations The waves in part ii) are traveling in a HIL dielectric of permittivity ##\epsilon_{r}## from ##0 <z<d## and then hit an ideal metal boundary at ##z=d##. The Attempt at a Solution I figure this...
  35. A

    Find the distance from the mirrors for 4 reflections

    Homework Statement Two plain mirrors are put parallelly and 20 cm from each other. A source of light is put between the mirrors, 5 cm away from one. Find the distance from the mirrors of 4 first reflections. Homework Equations a1=a2 The distance of the object from the mirror and the reflection...
  36. A

    With what speed does the object get nearer to the reflection

    Homework Statement An object gets closer to the plain mirror with a speed v. With which speed does it get closer to the reflection? Homework Equations l=v*t The Attempt at a Solution As l (length of road) is twice as big l2=2l1, but the time is equal t1=t2, then velocity should be two times...
  37. P

    Reflection dependence from wavelenght

    Homework Statement Hi guys, I have this exercise and I m confused. Incident (white light) light ray is perpendicular to glass surface , glass plate is 0,4microm thick. Which wavelengths in reflected ray becomes more intense? Homework EquationsThe Attempt at a Solution So i know that light is...
  38. Random Stuffs

    Why does light reflect at exactly 180 degrees?

    I understand the molecular principles behind the reflection itself, however it presents many problems, such as the one above. If you could explain it as easily as you can, I would be grateful. :)
  39. Zoey

    (Snell's Law) How do I find θi and θr?

    Homework Statement [/B]I am supposed to fill out a table with the values of θi and θr with the given information of n1 being 1.00 and n2 being 1.50 for the first row, and I am not quite sure how to do that just knowing the values that were given. I am also supposed to find the sine of θi and...
  40. M

    Reversal of Handedness by Reflection

    Hello everyone, I was just reading on circular polarization on Wikipedia and came across the sentence "The handedness of polarized light is also reversed when it is reflected off of a surface at normal incidence". I can see that the circular polarized wave should propagate in the opposite...
  41. E

    Complex numbers and reflection

    Homework Statement Reflection of the line ##\bar{a}z + a\bar{z} = 0## in the real axis is Homework EquationsThe Attempt at a Solution I know that a line in the complex plane is represented as ##\bar{a}z + a\bar{z} + b= 0## and that its slope ##μ = \dfrac{-a}{\bar{a}}##. I'm not sure how to do...
  42. vetgirl1990

    Thin films: reflection between glass plates

    Homework Statement Two parallel glass plates of index of refraction n are separated by an air film of thickness d. Light of wavelength λ in air, normally incident on the plates, is intensified on reflection when, for some integer m a) 2d=mλ b) 2d=mλ/n c) 2d=mnλ d) 2d=(m+1/2)λ e) 2d=mλ/2...
  43. S

    Lorentz tranformation of law of reflection

    Homework Statement Consider an inertial frame ##S## with coordinates ##x^{\mu}=(t,x,y,z)##, and a frame ##S'## with coordinates ##x^{\mu'}## related to ##S## by a boost with velocity parameter ##v## along the ##y##-axis. Imagine we have a wall at rest in ##S'##, lying along the line...
  44. A

    How to solve for angle of reflection in respect to floor?

    Homework Statement A student stands 2.7 m in front of a floor-to-ceiling mirror. Her eyes are 1.64 m above the floor and she holds a flashlight at a distance 0.85 m above he floor. Calculate the angle θ, in degrees, that the flashlight makes with respect to the floor if the light is reflected...
  45. 1

    B What causes reflection to occur in highly absorptive materials?

    I'm not sure if this belongs here however some of you may know the answer to my question. If I am correct, transparency occurs when light hits an object however the light does not reach the threshold frequency to energize an electron. Thus, the light does not get absorbed and is able to pass...
  46. G

    Total internal reflection, refractive index, optical fibres

    How does the claddibg with lower refractive index reduce the light loss from the core? Thank you.
  47. H

    Orbit invariant under reflection about apsidal vectors

    The book argues that since substituting ##\theta## by ##-\theta## leaves the orbit equation (3.34) unchanged, the orbit is therefore invariant under reflection about the apsidal vectors (Fig 3.12). If substituting ##\theta## by ##-\theta## leaves the orbit equation (3.34) unchanged, then there...
  48. V

    How Does Specular Reflection Support the Particle Theory of Light?

    I think this may have been done before. So people are aware of the geometry of reflection. If I go beyond, I try to say that if light can pump electrons, it is absorbed, if it merely polarizes, it gives rise to an alternating dipole supposed to be polarizing the region around in all directions...
  49. StanEvans

    Photon Reflection: Questions & Answers

    I was wondering while doing some work on the photoelectric effect about how it is that photons interact with their environment. The question that I have is why or how does a massless particle such as a photon reflect of a surface such as a mirror. My first thoughts went to collisions with the...
  50. Jadaav

    Designing a reflection sundial for the southern hemisphere

    Hello, My aim is to build a small reflecting sundial as designed by Sir Isaac Newton. I found from a website that it consists of a ceiling and a small mirror. What I want to know is how it works, the concepts behind it and how to build one. It's for an undergraduate project that I've got...
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