Final answer:
The net radiation leaving Disk 1 is the same as that leaving Disk 2 because both disks are at the same temperature and the properties of a black body with respect to radiation in vacuum apply to both objects in thermal equilibrium.
Step-by-step explanation:
The net radiation leaving Disk 1, which is a black body, is the same as that leaving Disk 2, assuming both disks are maintained at 25 degree C and are in a vacuum. This is based on the properties of black bodies and diffuse and opaque objects in thermodynamic equilibrium. According to the Stefan-Boltzmann law, the power radiated per unit area of a black body is proportional to the fourth power of the temperature, as described by the equation: P = σeT^4, where P is the power radiated per unit area, σ is the Stefan-Boltzmann constant, e is the emissivity, and T is the temperature (in kelvins).
Since both disks are at the same temperature and are in thermal equilibrium, their emissivities will not change the net radiation transfer between them, regardless of their surface characteristics. As such, they both emit the same amount of radiation into the vacuum.