UVC rays:
... are even more short waved and energetic as it is with UVA and UVB rays. UVC rays cover the main part of the whole UV spectrum. They have a strong germicidal (bactericide) effect.
As it is with the visible rays of light, UVC rays are only moving straight-lined and dramatically loose their intensity the further they get from the source.

UVC rays do not penetrate materials (even no window glass or transparent foil) and have only an effect where they strike.