✔ 最佳答案
UV lamp output refers to the UV power at close proximity to the lamp. You could take the distance to be about 1 cm. Hence, the power is much higher that that measured at 1 metre.
Be aware that the inverse square law doesn't not apply here because at close distance, the lamp cannot be regarded as a "point source". Hence, if we use the inverse square law to calculate the power output at 1 metre (100 cm), this turns out to be 7500/100^2 uw/cm^2 = 0.75 uw/cm^2, which is lower than the actual measured value of 57 uw/cm^2.
2012-02-21 14:17:58 補充：
Your suppl question:
Yes, you could regard the figure as measurement near the surface of the uv lamp. As said in my answer, because the lamp cannot be taken as a point source, inverse square law doesn't apply. In fact, the uv intensity falls off less than that calculated by using inverse square law.
2012-02-21 14:22:20 補充：
(cont'd)... The intensity value given at 1 metre enables intensity as farther distances to be calculated. As at distances of a few metres away, the point source approximation can apply,...
2012-02-21 14:22:40 補充：
(cont'd)... and intensity can now be calculated using inverse square law based on the given intensity at 1 metre. This is the use of that value.
