Lifetime of Light Inside a Mirrored Sphere

Most recent answer: 04/10/2015

Why will light NOT keep reflecting inside of a mirrored sphere when the source is turned off? Say, for instance, inside a totally mirrored and circular sphere. In other words, will light keep reflecting off the walls or a totally mirrored sphere?
- stephen zdradzinski (age 72)
welcome, md, usa

Hello Stephen,

In principle if the mirror surfaces were 100% reflecting the light would bounce around forever.  Unfortunately there is no such thing as a perfect mirror.   Ordinary silvered mirrors have reflection coefficients of 95% or so. That means after 10 bounces or you have only about 60% of the light left.   And so on...


(published on 04/10/2015)