Distance from light(or other electromagnetic)source

[slyth]

Hello.I'm doing a research on ultraviolet (mainly on UVB band).
UVB band with the wavelength 280nm~315nm has the energy of 4.43eV~3.94eV
which can be calculated from Plank-Einstein equation.

In visible spectrum,light intensity can be calculated from
$$E_{r}=\frac{E_{0}}{4\pi r^{2}}$$
With the above equation,when E(r) and E(0) is known,distance,r can be calculated.
Light radiation is measured in mW/cm^2,and I right?

So,my question is,using the above equation,instead of light radiation,
is it possible to calculate distance by replacing E(r) and E(0) with energy [eV] ?
Where E(r) and E(0) can be obtained from UV sensor readings.
Radiometers do measure UV intensity in mW/cm^2. I'm trying something different.

 

[HallsofIvy]

Yes, of course, that's a simple algebra calculation.

Multiply both sides of the equation by $r^2$ and divide both sides by $E_r$ to get
$$r^2= \frac{E_0}{4\pi E_r}$$
Now take the square root of both sides:
$$r= \sqrt{\frac{E_0}{4\pi E_r}}$$
We use the positive root because distance is always positive.