Those bottles of light...

[Externet]

Shown on some reports of third world innovative diy gadgets, they have a led lighting a water filled soda bottle. (This is not the 'skylight' similar approach that funnels sunlight and rain leaks into a dwelling)
How does the addition of the soda bottle optical losses improves illumination than the bare led alone ?
The difference I see is it creates a non-point of light emission by being a bottle-sized body of emission with some according gentler pupil reaction.

Now, the "old" battery mentioned.  Why old ?

 

Next, about the skylight bottle.  Why is it perceived better than a transparent piece of roofing ?  Is it from the strong habit in modern offices/homes to cover windows with draperies and then turn on the lights ?

 

[swansont]

45 minutes ago, Externet said:

 Now, the "old" battery mentioned.  Why old ?

Because you don’t need a new one, probably.

45 minutes ago, Externet said:

Next, about the skylight bottle.  Why is it perceived better than a transparent piece of roofing ?  Is it from the strong habit in modern offices/homes to cover windows with draperies and then turn on the lights ?

It does a better job of dispersing the light. 

[Sensei]

"The device is simple: a transparent two-liter bottle is filled with water plus a little bleach to inhibit algal growth and fitted into a hole in a roof."

https://en.wikipedia.org/wiki/Liter_of_Light