Why are intensity and irradiance interchangeable here?
williampeng20
I think it's because we have a light source so we do have radiant intensity, but for the purposes of seeing how this intensity changes over distance, we can use irradiance to measure this intensity by creating dummy spheres as points of irradiance at different radiuses.
kingdish
Note that the denominator here is r2. So the intensity of light falls off really quickly as it travels further away from its source.
orkun1675
@kingdish yes this makes sense in every day life as well. This reminded me of the force of gravity which is also proportional to 1/r2.
mnicoletti15
Id hugely appreciate if someone could let me know if this is correct or not: We can think of this light source as a point charge, and we can think of the irradiance as the "electric field" from this point charge? And then if we integrate the irradiance over a surface we get back the flux?
sirejdua
Flux can be thought of as the amount of flow through a surface. In that sense, electric field and irradiance can be thought of to be analogous, since integrating both over a surface yields the flux through that surface.
avinashnandakumar
How does the irradiance units work? If its flux over area, how do the steradians term fit into it?
Why are intensity and irradiance interchangeable here?
I think it's because we have a light source so we do have radiant intensity, but for the purposes of seeing how this intensity changes over distance, we can use irradiance to measure this intensity by creating dummy spheres as points of irradiance at different radiuses.
Note that the denominator here is r2. So the intensity of light falls off really quickly as it travels further away from its source.
@kingdish yes this makes sense in every day life as well. This reminded me of the force of gravity which is also proportional to 1/r2.
Id hugely appreciate if someone could let me know if this is correct or not: We can think of this light source as a point charge, and we can think of the irradiance as the "electric field" from this point charge? And then if we integrate the irradiance over a surface we get back the flux?
Flux can be thought of as the amount of flow through a surface. In that sense, electric field and irradiance can be thought of to be analogous, since integrating both over a surface yields the flux through that surface.
How does the irradiance units work? If its flux over area, how do the steradians term fit into it?