What is Reflectance: Definition and 39 Discussions

The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic structure of the material to the electromagnetic field of light, and is in general a function of the frequency, or wavelength, of the light, its polarization, and the angle of incidence. The dependence of reflectance on the wavelength is called a reflectance spectrum or spectral reflectance curve.

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  1. aferrie

    I Help with sourcing a specific type of integrating sphere

    I am looking for a specific type of integrating sphere that can be used to capture diffuse reflectance measurements, and I would appreciate help with locating a commercially availably version of this sphere. The diagram below illustrates the type of sphere I am looking for [1]. Two ports are...
  2. aferrie

    I Measuring reflectance of a non-planar object w/ an integrating sphere

    I am designing an experiment to measure the reflectance (diffuse+specular) of insect specimens, and I plan to use an integrating sphere to collect the measurements. Typically, I have seen that reflectance measurements with integrating spheres are done with planar (i.e. flat) sample objects. So...
  3. K

    B Calculating non-dielectric reflectance without using complex numbers

    I need a to calculate the fresnel reflection ratio of a non dielectric material given the incident angle, the refractive indexes of the incident and interfacing materials and the extinction coefficient of the interfacing material. I need to to this without directly using complex numbers, due to...
  4. LCSphysicist

    Understanding Reflectance and Transmittance Calculations

    This type of problem always confuse me. Indeed, i am always skeptical with the answer i get, because i know there is some subtle points in the calculations that maybe i am missing... Anyway: Can we just say that $$T = 1 - R = 1 - \frac{(R_{\parallel}+R_{\bot})}{2} = 1 -...
  5. xp2334

    Colorimeter transmittance and reflectance questions

    qns 1 attempt: In reflectance mode, measurements are taken based on the amount of light reflected from the surface of the sample. Therefore, in clear/translucent fluids, it is critical to have appropriate backing material behind the sample, such as a white and matte piece of paper or cardboard...
  6. T

    A Reflectivity with gradient in refractive index

    Hey all. Was wondering if anyone knew how I would go about determining the amount of reflectance that occurs when there is a gradual change in the refractive index. For example, if I have a material in air whose refractive index begins at e_r=1 (i.e. it matches the refractive index of the air)...
  7. mcas

    Evaluate reflectance of an aluminum mirror

    Note: for some reason frequency on this lecture is indicated by \omega. I wanted to calculate the reflectance using one of these equations that were given to us during the lecture: R=1 where \omega < \omega_p...
  8. XonDoi

    How Does VIS-NIR Reflectance Linearity Vary in Mixed Color Pigments?

    Hi everyone, I am a student studying color pigment fingerprints and how we can improve their identification. Especially in cases where these are mixed with each other to create variants. We are using the VIS and NIR regions (400-1000nm) to obtain our observations. I have a few questions...
  9. brainpushups

    Measuring Reflectance with a Digital Camera

    Background: This fall our initial plan will have high school students on campus 1 day per week and working remotely for the remainder of the week. I'm trying to plan for some at-home labs and projects. I came across http://albedodreams.info/how_to/how-to-calculate-albedo-yourself/ site which...
  10. Athenian

    Fresnel Equations for the Power of Reflectance and Transmittance

    I understand that the power of reflectance and the power of transmittance (regardless of it being S-polarized or P-polarized light), when added together, would equal to one. In other words, ##R+T=1##. However, how do I go about checking for this fact? Using the equations from the "Relevant...
  11. E

    Relationship between Reflectance and Albedo

    I have a question regarding the relationship between the reflectance and albedo of a material. What I Know: Both quantities are the ratio between the incoming and outgoing radiation from a material. Correct me if I am wrong, the reflectance of a material depends on the material while the albedo...
  12. 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...
  13. sounouhid

    A How to Convert Diffuse Reflectance to Absorption Spectrum in FT-IR Spectroscopy?

    Hello every one How can i convert a spectrum plotted in Diffuse reflectance units to an absorption spectrum in FT-IR spectroscopy knowing that I've a diposed a thin layer of TiO2 into an ITO substrate. thank you
  14. Carlos de Meo

    Heat exchange, emissivity and reflectance

    Hi Guys I´m studying the heat exchange problem in furnaces and, to begin with, i started with Incropera´s book. One thing is actually driving me crazy On the last part of this exercise´s solution (part 3), the physical principle involved is not very clear to me. To calculate the absorptivity of...
  15. nmbr28albert

    I Reflectance of metals at low frequencies

    When calculating the dielectric constant of metals using the Drude model, in the low frequency regime (infrared and beyond) one gets an approximately pure imaginary value: $$\epsilon(\omega) \approx i\frac{4\pi n e^2\tau}{m_e\omega}$$ which gives an absorption coefficient: $$\alpha(\omega)...
  16. E

    A Question about Radiance, Solar Flux and Reflectance

    I stumbled upon this equation for a Lambertian uniform target: ##\rho^{*} = \frac{\pi L}{\mu_s E_s}##, where ##\rho^{*}## is the reflectance, ##L## is the measured radiance, ##E_s## is the solar flux at the top of the atmosphere, and ##\mu_s## is the cosine of the sun zenith angle...
  17. M

    Exact solutions for reflectance, transmittance, absorption?

    I'm measuring transmittance through and reflectance from thick glass samples, using spectrophotometers. Does anyone know if there's an exact solution for the surface transmittance r, surface reflectance t, and absorption coefficient A (as in Beer-Lamberts law). For a specific wavelength the...
  18. I

    Urban heat effect: high solar reflectance and emittance

    Homework Statement "The urban heat island (UHI) effect refers to the phenomenon of a metropolitan or built up area which is significantly warmer than its surrounding areas." Using white paint in roofs increases the solar reflectance and decrease the thermal intake into a building. Question:-...
  19. S

    Reflectance Equal to Transmittance

    Homework Statement Under what conditions would the reflectance, R, and the transmittance, T, be equal to each other at normal incidence at an interface? What would be the values of R and T under these conditions? Homework Equations Rs = |rs|2 Ts = |ts|2 η2cosθt / η1cosθi Rs + Ts = 1 rs =...
  20. F

    Reflectance or reflectivity spectrum interpretation

    Hello forum, The reflectance spectrum has % on the vertical axis and wavelength on the horizontal axis. A red object is red because it reflects all the red light and absorbs all the other wavelengths of the white incident light. If the read object was ideal, would its reflectance spectrum be...
  21. C

    Calculation of phase shift from reflectance data

    Hi, do you know how i can calculate the phase shift of measured reflectance data? I find the dispersion relation formula but I can´t solve it. I know that this dispersion formula is split in three terms. The first term has a range form 0 to w_min, the second term from w_min to w_max and the...
  22. M

    How to calculate refractive index from reflectance values

    Greetings. how to calculate the refractive index, extinction coefficient, absorption coefficient values from the reflectance data. And also suggest me how to measure the transparency of glass. Is there any relation between transparency and refractive index Thanks in advance
  23. P

    Do Spectral Reflectance Curves Change with Different Surrounding Media?

    Hello, Are spectral reflectance curves dependent on the interface between the reflector and surrounding medium? For example would they be different if I had a silver mirror in air compared with silver mirror in a semiconductor? I think they would be because of the refractive index contrast...
  24. H

    Strange reflectance from periodic structure

    Hi, last semester I did a project with two fellow students. We made a numerical model to calculate the reflectance from a periodic V-shaped structure of silicon similar to this: In the course of doing so, we came across something we could not explain. I have placed an image of it below...
  25. H

    What Causes Peaks in Reflectance Graph of Polished Silicon Wafer?

    Hi all When one measures the reflectance of say silicon, certain peaks appear in the graph. I am wondering, if anyone can explain the location of the peaks and their meaning. Here the graph is, I hope the picture thing works, else here is the link. The graph is for a polished...
  26. H

    What do the peaks in the reflectance spectrum of silicon samples represent?

    Hello, I am currently analysing some relfectance data I obtained from measurements on several silicon samples. During the process I used the standard fresnel coefficients, and suddenly I began to wonder, what the peaks describe? The last graph at this link shows it for normal incident light...
  27. P

    Is there a way of measuring reflectance vs absorbance

    I am looking at EMI Shielding effectiveness testing and I would like to measure how a material is shielding Electromagnetic waves, qualitatively. Is there a way to measure how a material is shielding qualitatively and quantitatively (in dB)?
  28. L

    Measuring the reflectance of a surface?

    Guys, was hoping to get some feedback on a measurement of reflectance I was hoping to conduct. Generally in published work I see that reflectance is plotted vs. wavelength, and most of these measurements are done with equipment such as integrating spheres etc for diffuse reflection etc. I...
  29. R

    What is the Effect of Nanotube Length on Reflectance in Nanotechnology?

    hi guys, I'm working about nanotechnology, and my current research is about nanotubes. Based on my observation, as the nanotubes length increased the reflectance also increased, one of my possible explanation is that; since dielectric constant is dependent on the dimension of the material, and...
  30. S

    Complex amplitude reflectance of a spherical mirror

    Homework Statement Prove the complex amplitude reflectance of a spherical mirror is given as exp[-jk(x2+y2)/R] Homework Equations Transmittance of a spherical mirror is also exp[jk(x2+y2)/2f] The Attempt at a Solution I have totally no idea how to go about doing this. Can I just...
  31. P

    Basic question about measurement of thin film by means of spectral reflectance

    Hallo alle users, as the title indicates, I have a question about measurement of thin film thickness by means of spectral reflectance. Given, the to be measured thin film has thickness less than 600 nm, but the measuring light has only wavelengh larger than 600 nm. Does it mean, that the...
  32. S

    How extract phase angle from reflectance using Kramers-Kronig

    I try to extract optical constants (complex refractive index) from the spetral reflectance data - R(omiga), the common method is using Kramers-Kronig relations to calculate the Phase information of the reflection - Psi(omiga), then according to the normal reflection coefficients, the complex...
  33. 8

    Reflectance and Transmittance of Light in Water-Glass Interface

    Homework Statement There's a block of glass and it has a refractive index n = 1.5 and it is put in water. Randomly polarized light is incident from the water towards the glass at an angle of 53 degrees to the normal. a) what % p-polarized (part) of the em wave (light) is reflected off...
  34. M

    Calculate the total reflectance on a surface

    Hi, I have a structure and I can calculate the reflection from the surface (S11 or S21)with different incidence angle. Now I would like to calculate the total reflectance of the hemisphere above the surface.. how can I integrate them all ?
  35. G

    Reflectance to Status A Density; How to convert?

    I have calibration data for some 0/45 reflectance standards which is in spectral format of %R in 10nm increments. I need to check the accuracy of reflection densitometers which read Status A density (V,R,G,B). What is the proper way to convert the spectral reflectances to density? Thanks, GR
  36. H

    Absorption and reflectance spectrums

    hey, just wondering, what's the relationship between absorption and emissions spectra (i.e. would they absorb and reflect the same wavelengths or complement wavelengths of radiation?) thanx, hechnal
  37. A

    Light Reflectance: Explaining Specular Reflection

    Good morning! I am trying to understand the mechanism of light reflectance in a quantum context. Diffused light seems to be straightforward, however I cannot find a simple (if such a thing exists) explanation regarding specular reflection. What is the interaction between the photons and...
  38. D

    What are reflectance spectra and synchronous spectra?

    What are reflectance spectra and synchronous spectra? What are the difference and which information I can obtain from them ?
  39. M

    Finding the Gold Coating Thickness for 50% Transmittance and 50% Reflectance

    Does anyone know the thickness of a gold coating that would give me 50% transmittance and 50% reflectance? Thanks, Simon
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