Definition of Intensity of Radiation

  • Thread starter Thread starter Greg Bernhardt
  • Start date Start date
  • Tags Tags
    Intensity
AI Thread Summary
Intensity of radiation is defined as the power per unit area that is perpendicular to the direction of radiation, represented as a vector. It can also be expressed as the product of energy density and velocity, often referred to as energy flux. The standard unit of measurement for intensity is watts per square meter (W/m²). For surfaces perpendicular to radiation, intensity is calculated using the formula I = P/area, while for general surfaces, it involves integrating the dot product of intensity and the surface normal. Understanding these concepts clarifies the relationship between power, area, and energy density in the context of radiation.
Messages
19,787
Reaction score
10,738
Definition/Summary

Intensity of radiation = power per area perpendicular to the radiation. It is a vector, parallel to the radiation.

Intensity of radiation = energy density times velocity (therefore sometimes called energy flux).

It is measured in watts per square metre (Wm^{-2})

Equations

For a surface perpendicular to the radiation:

I\ =\ P/area

For a general surface, with normal \hat{\mathbf{n}}:

P\ =\ \int_S \mathbf{I}\cdot\hat{\mathbf{n}}\,dS

Extended explanation

Power per area = energy density times velocity:

Power = energy per time (measured in W\ =\ Js^{-1}).

Power per area = energy per area per time = energy density (ie, per volume) times velocity.

So intensity = power per area = energy density times velocity.

* This entry is from our old Library feature. If you know who wrote it, please let us know so we can attribute a writer. Thanks!
 
Physics news on Phys.org
Thanks for the explanation on intensity. That makes it much clearer.
 
So I know that electrons are fundamental, there's no 'material' that makes them up, it's like talking about a colour itself rather than a car or a flower. Now protons and neutrons and quarks and whatever other stuff is there fundamentally, I want someone to kind of teach me these, I have a lot of questions that books might not give the answer in the way I understand. Thanks
Back
Top