Encyclopedia … combined with a great Buyer's Guide!


Definition: the ratio of transmitted optical power to the incident optical power at some partial transparent object

German: Transmissionsgrad, Transmissionsvermögen

Category: general optics


How to cite the article; suggest additional literature

URL: https://www.rp-photonics.com/transmittance.html

The term transmittance is defined as the ratio of transmitted optical power to the incident optical power for some object, for example an optical system. For transmission through flat unstructured surfaces, it is the same as the transmissivity. However, the transmittance is a more general term and can be specified in a wider range of situations:

  • Some objects can cause scattering of light. One may then specify the hemispherical transmittance, which is based on the total transmitted radiant flux. Also, there is the directional transmittance, defined as the ratio of transmitted and incident radiance; it is a function of observation angle.
  • There are extended objects, where light can penetrate, is internally scattered and thus partially transmitted and partially reflected. The transmittance simply quantifies the amount of light getting through the object, on whatever ways.
  • When light is incident on a transparent plate with parallel surfaces, for example, Fresnel reflections occur on both surfaces. The transmitted power can be affected by interference effects, making the transmittance strongly wavelength-dependent.

The results of transmission measurements with spectrophotometers, for example, are usually called transmittance rather than transmissivity, since one is often dealing with extended samples.

See also: transmissivity, reflectance, absorbance

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here; we would otherwise delete it soon. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him, e.g. via e-mail.

Your question or comment:

Spam check:

  (Please enter the sum of thirteen and three in the form of digits!)

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.


Share this with your friends and colleagues, e.g. via social media:

These sharing buttons are implemented in a privacy-friendly way!

Code for Links on Other Websites

If you want to place a link to this article in some other resource (e.g. your website, social media, a discussion forum, Wikipedia), you can get the required code here.

HTML link on this article:

<a href="https://www.rp-photonics.com/transmittance.html">
Article on Transmittance</a>
in the <a href="https://www.rp-photonics.com/encyclopedia.html">
RP Photonics Encyclopedia</a>

With preview image (see the box just above):

<a href="https://www.rp-photonics.com/transmittance.html">
<img src="https://www.rp-photonics.com/previews/transmittance.png"
alt="article" style="width:400px"></a>

For Wikipedia, e.g. in the section "==External links==":

* [https://www.rp-photonics.com/transmittance.html
article on 'Transmittance' in the RP Photonics Encyclopedia]