# Distance from light(or other electromagnetic)source

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?

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
Multiply both sides of the equation by $r^2$ and divide both sides by $E_r$ to get
$$r^2= \frac{E_0}{4\pi E_r}$$
$$r= \sqrt{\frac{E_0}{4\pi E_r}}$$