Coffee addiction? Nothing else left?

I didn’t write it out, but what I was trying to get at was that if it would “slow down”, then it would be slower on the other side. The explanation that the light travels longer through a medium with the same speed would therefore make sense to me.

But then again, how it wouldn’t shoot out in every direction, that doesn’t make sense to me.

I don’t know much about light, that’s why i’m asking. And i’m sure some article or paper would have anwers for that question, I might search it on my own.

If you fire a laser that goes first through vacuum, then through a lens, then again in vacuum, at what speed is the light travelling on the other side?

I think most things you can make yourself, if you’re talented enough. Might take a lot of effort though. But afterall, someone made everything in the first place.