Special relativity is replete with examples of turning mirrors into clocks. Place two mirrors across from one another, bounce light between them, and measure the time. But as I thought about this, when a photon hits the mirror, it is absorbed by an electron which moves to a higher energy state, and then released as the electron moves back to the lower state, and this must take time. So the time it takes light to move to a mirror and back is the twice the distance to the mirror divided by c PLUS the time for absorption and re-emission. I've never seen that adjustment anywhere, which tells me I am either thinking about this wrong, or places like Ligos are actually making this type of adjustment when they bounce light back and forth between mirrors to measure gravity waves. Can anyone add some insight into what I'm missing?