Glass: Increase "Transmission Roughness" as the object behind goes far In the real world, there are some rough glasses that as objects behind them go away, they (the objects) become more blurry, but when we stick an object just behind this type of glass, it's almost shown clear (also some materials has this property in their reflections, that's another question).

For clarification, I photographed these examples:


When the object (my hand) is stuck behind the glass:



When the object goes a little far from the glass:

Bringing it farther:




How do you achieve this effect in Blender with Cycles engine? (mine is Blender v2.82)
Cycles is physically based so you don't need to add anything to a regular transmissive shader.
Add a Principled BSDF to you plane. Set the transmission to 1. You can tweak the IOR but the default value of 1.45 is fine for the purpose.

The setup:



Result :