Processing math: 100%
Skip to main content
Library homepage
 

Text Color

Text Size

 

Margin Size

 

Font Type

Enable Dyslexic Font
Physics LibreTexts

4.6: Radiation Pressure

( \newcommand{\kernel}{\mathrm{null}\,}\)

Recall equation 1.18.5 and the conditions for which it is valid. It was derived for isotropic radiation. In the atmosphere, radiation is not isotropic; there is a net flux of radiation outwards. Therefore the radiation density must go inside the integral sign. We can also write the equation in terms of specific intensity, making use of equations 1.15.3 and 1.17.1. The equation for the radiation pressure then becomes

P=1c4πIcos2θ dω,

where by now we are used to the abbreviated notation.

If the radiation is isotropic, this is not zero; it is 4π/(3c). In the expressions for J and for P, the power of cosθ is even (0 and 2 respectively) and one can see both physically and mathematically that neither of them is zero for isotropic radiation. One the other hand, the expression for F has an odd power of cosθ, and it is therefore zero for isotropic radiation, as expected.


This page titled 4.6: Radiation Pressure is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Jeremy Tatum via source content that was edited to the style and standards of the LibreTexts platform.

Support Center

How can we help?