What is difference between intensity of radiation and energy of radiation?

So yeah? And what is intensity of radiation because I know how to calculate energy of for example a isotope that sends out y-radation but not what or how to calculate the intensity?What is difference between intensity of radiation and energy of radiation?
Intensity is the amount of energy per unit time passing through a unit area perpendicular to a radiation source. Energy per unit time is the power, so intensity is the power passing through a unit area.

The power (P) of a source is simply the energy of the decay particles multiplied by the activity (the number of decays per second).

Now think of the source being surrounded by concentric spheres. The surface area of a sphere with radius r is given by 4*蟺*r^2. The radiation emitted by the source has to pass through these spheres, so the intensity at a distance r is given by:

I(r) = P/(4*蟺*r^2)

This has units of power per unit area, which is the appropriate unit for intensity.

(Note that it is also possible to define radiation intensity as the power per unit solid angle, in which case the intensity does not vary as a function of distance. This is a definition used commonly when talking about the electromagnetic radiation emitted by antennas.)

-----------------------

Note added in response to question in new "addional details"...

The usual definition of intensity is the (energy carried by the decay particles crossing a unit area) x (the activity, i.e., energy * activity/area. Alternatively, you can think of this as the flux of particles (particles crossing a unit area per unit time) multiplied by the energy of the particles.

If you are far enough away from the source (or the source is small enough), you can consider the source as a point source. Then, the pattern of radiation emitted by the source can be considered to be spherically symmetric, and the total area through which the particles must pass is 4*蟺*r^2 (the surface area of a sphere of radius r).

The intensity varies as a function of distance from the source; specifically, it varies as 1/distance^2.