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Q & A: Seeing photons?

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Most recent answer: 04/21/2008
Q:
Two mirrors are aimed directly at each other a light year apart across a vacumn. A photon passes close in front of one mirror. Will its reflection be delayed in the second mirror?
- John Aho (age 66)
Sequim, WA ,USA
A:
I'm not sure I understand your question.    In order for a photon to be 'seen', it has to interact with something, like a photographic plate or a cell in your retina.  In doing so, the photon ceases to exist.    Now the photon in question could possible be reflected from the far away mirror and return, two years later, and then be detected.  It could also bounce off the near mirror, bounce off the second mirror and then be detected; same two year delay plus a few picoseconds.

LeeH

(published on 04/21/2008)

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