UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
How it Works
Ask a Question
Search Topics
Our Scientists
Science Links
Contact Information
I need help in answering a question.  If light travels until striking an object, but a mirror reflects light, would not a light travel forever inside a mirrored sphere? 
Question Date: 2020-03-16
Answer 1:

The answer to your question is that in theory yes, but in practice, no. All the mirrors we can make are not 100% reflective; they still absorb some light. The sphere would also need to contain a perfect vacuum inside, which means no air inside. The oxygen and nitrogen molecules in air can absorb light and convert it into heat.

Setting up an experiment where we could create a perfect sphere, with a perfect mirror inside, then also introduce light without letting air would be basically impossible since we cannot create a perfect sphere nor absolute vacuum. In the hypothetical scenario where we could do all these things, then from a classical perspective the light should bounce around forever inside. There may be some relativistic or quantum effects that still cause the light to stop bouncing around, but I don't know enough about those topics to explain anything more.


Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use