What is the difference between pressure of radiation and pressure of diffuse radiation

see attached file

https://phys.libretexts.org/Bookshelves/Astronomy_and_Cosmology_TextMaps/Map%3A_Stellar_Atmospheres_(Tatum)/01%3A_Definitions_of_and_Relations_between_Quantities_used_in_Radiation_...

In the above formula, you are right that u is same as energy density, P can be equal to U/3 or U/2 or U or 2U, depending upon circumstances, you can refer link attached for detaile...

Radiation pressure : When an electromagnetic wave incidents and hits on the surface of the object,it will exert a force at its surface area and the pressure formed due to this is k...

i think both should be same ....but let me check once

mam, they given that pressure of diffuse radiation=p=u/2=energy density/3.actually both u and energy dencity are same. then why they given so

Diffusion pressure : It is a hypothetical term coined by Meyer (1938) to denote the potential ability of the molecules or ions of any substance to diffuse from an area of their hig...

Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum ...