What is watt per steradian? - Definition from WhatIs.com

Definition

watt per steradian

Part of the Electronics glossary:

The watt per steradian (W · sr -1 ) is the standard unit of radiant intensity. Reduced to base units in the International System of Units ( SI ), it is the equivalent of a kilogram meter squared per second cubed per steradian (kg · m 2 · s -3 · sr -1 ).

A point source of electromagnetic (EM) power that radiates equally well in all directions, and whose output is 1 W · sr -1 , has a total output power of 4 p (approximately 12.5664) watt s (W). This is because there are 4 p steradians in three-dimensional space with respect to a point of reference. The watt per steradian can be used to define the radiant intensity at any EM wavelength , from low-frequency radio waves through the gamma-ray spectrum. For visible light, in the wavelength range of approximately 390 to 770 nanometers (nm), the lumen is the preferred unit.

Suppose an electromagnetic field having P watts of total power is radiated from an isotropic emitter (that is, a point source that radiates equally well in all directions). Then the radiant intensity, P' , in watts per steradian is given by the following formula:

P' = P / (4 p )

Also see electromagnetic field , lumen , power , International System of Units ( SI ), steradian , and watt .

This was last updated in September 2005
Posted by: Margaret Rouse

Related Terms

Definitions

  • modulation

    - Modulation is the process of adding information to a steady waveform or to an electronic or optical carrier signal, usually applied to electromagnetic signals. (SearchNetworking.com)

  • resistance

    - Resistance is the opposition that a substance offers to the flow of electric current; the term contrasts with conductance, which is a measure of the ease with which current flows through a substance. (WhatIs.com)

  • electric field strength

    - Electric field strength is a quantitative expression of the intensity of an electric field at a particular location. (WhatIs.com)

Glossaries

  • Electronics

    - Terms related to electronics, including definitions about electrical components and words and phrases about computers, laptops parts, digital cameras, televisions and home appliances.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question About watt per steradianPowered by ITKnowledgeExchange.com

Get answers from your peers on your most technical challenges

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.