There is a lot simpler test for UV-C using a green banana. See this blog.
https://rustybolt.info/wordpress/?p=13488
There are lots of UV lights being advertised on social media that use LED lights and claim to sterilize the Corona Virus. These are not putting out UV-C light which is necessary for killing germs. This video shows that the LED lights put out no UV-C, but put out UV-A or UV-B. Beware, bbecause these fake lights are not killing the germs, and you can get CoViD19 after using a fake one!
If the reading goes down a lot when he puts in the glass, it means the light is putting out UV-C and the glass is blocking it. If the reading stays the same when he puts the glass in, there was no UV-C put out by the light, so the glass has nothing to block and the reading changes very little.
