Q.
Frosted glass is widely used for translucent windows. The region, where a transparent adhesive tape is stuck over the frosted glass becomes transparent. The most reasonable explanation for this is
Frosted glass has a rough layer which causes irregular refraction and makes glass translucent.
When a transparent tape which has refractive index close to that of glass is pasted over the rough surface of glass, the tape glue fills the roughness of glass. This makes glass surface more smooth and so refraction is more regular. This makes region of tape transparent.