Dear Derek, Good question but ...

Dear Derek,

Good question but complex issue, for ​calculation of  the ​UV-dose (mW/cm2)​ or J/m2. Scientists have known for nearly a century that ultraviolet light of certain wavelengths is an effective germicidal agent. However, production of ultraviolet light in the proper range  expensive. With the development of high-intensity, long-life lamps came renewed interest in the use of ultraviolet as a disinfection agent for a variety of liquids, but primarily water.

UV can be measured and it can be controlled. If UV is UV can be measured and it can be controlled. If UV is not measured & controlled not measured & controlled it will cause mysterious it will cause mysterious problems

Following parameters are require

1. Dwell Time or Belt/Line Speed Dwell Time or Belt/Line Speed
2. Hour Meter
3. Electrical Power (amp meter)

E= hc/λ

Where h= Planck Constant (6.626 x 10-34 m2 kg/s); c = speed of light in vacuum (3 x 108 m/s); λ (Lambda) = wavelength of the radiation, in this 365nm, which is equals to 3.65 x 10-7 m.

So, E = 6.626 x 10-34 x 3 x 108)/ 3.65 x 10-7 = 6.626 x 10-34 x 3 x 108)/3.65 x 107 = 5.446 x 10-19

Units = [(m2 kg/s) (m/s)]/(m) = (m2 kg/s x m/s) x (1/m) = m2 kg/s2 = J

E = 5.446 x 10-19 J

For understand problem following example may be considering

duration: 7 x 24 x 60 x 60 = 604800 s

E = 5.446 x 10-19 x 6.048 x 105 = 3.294 x 10-13 J (this much radiation is falling on metre square, but your source is 5 cm is away)

Consideration of squared law as your source is.

5 cm = 0.05 m, which means radiation only covers (0.05)2 = 0.0025 m2

This means you have to divide the above equation by 1/0.0025 = 400 so as to make it in 1 m2 , as below

E = 3.294 x 10-13/400 = 8.235 x 10-16 J

ANSWER = 8.235 x 10-16 J at 365nm

Others are

9.953 x 10-16 J at 302nm

1.183 10-15 J at 254nm