Subject: How fast does light dissipate in a 2 way spherical mirror?

I realize that a two way mirror does let light pass through both ways - 
just at a lesser level on one than the other.  Let's state that it is 
possible to create a perfectly spherical 2 way mirror ball with the 
reflective surface (silver nitrate?) on the inside.  Let's also state that 
we have a camera with a framerate in the billions per second area.  Now we 
were to shine a high powered light source into the ball then turn it off.  
Upon viewing the playback, would the ball seem to slowly get dimmer as the 
light dissipated or would it instantly lose light at the same time the 
source did?  If it were to slowly dissipate, what if you were able to 
place that ball into another sphere that instead had a pure mirroring 
surface on the inside before ALL the light dissipated - would it be able 
to "store" light, even if just for a moment?  Would it have to be a vacuum?

Re: How fast does light dissipate in a 2 way spherical mirror?