Two solid spheres of radii `R_(1)` and `R_(2)` are made of the same material and have similar surfaces. These are raised to the same temperature and then allowed to cool under identical conditions. The ratio of their initial rates of loss of heat are

Two solid spheres of radii 5cm and 3cm are made of same material and have similar surface. The spheres are raised to the same temperature and then allowed to cool under identical conditions. The ratio of rate of fall of temperature is

Two solid spheres of radii R_(1) and R_(2) are made of same material and have similar surface. The spheres are raised to the same temperature and then allowed to cool under identical conditions. Assuming spheres to be perfect conductors of heat, their initial ratio of rates of loss of heat is:

Two spheres of radii R_(1) and R_(2) are made of the same material and are at the same temperature. The ratio of their thermal capacities is:

A sphere and a cube both made of copper have equal volumes and are blackened. These are heated to same temperature and are allowed to cool under same surroundings. The ratio of their rates of loss of heat is