Wireless signal strength

My question is possibly somewhat misplaced, but I'll try to explain as best as I can. Suppose I have a transmitter with a frequency of 2500MHz and a power of 1W. It radiates uniformly in all directions. Consider a situation in 2D. Suppose that at a distance of $d_1$ there is an object. How could the strength of the signal on the other side of that object be calculated? Suppose we know $d_1$, as well as the distance the signal passes through the object ($d_2$ - this would be the distance gained if a straight line is drawn from the transmitter location to the location where the power is to be calculated, and then measured from the point it enters the object to the point it exists the object). Also, we know the distance from the object to the point where we want to calculate the strength ($d_3$). Also, assume that the attenuation factor of the object is $\alpha_o$, and the attenuation of "air" is $\alpha_a=1$.

I know that the $P \propto \frac{1}{d^2}$, but how to include the attenuation?

I'm currently calculating power as:

$P_d = \frac{4 \pi P_0}{f^2 d^2}$

where $P_0$ is the transmitter power, $f$ is frequency and $d$ is distance from transmitter.

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