Activity

Right. I need to delete that “index” next time. It only works inside the notebook itself.

Oops, another ambiguity in the problem statement. The observer is supposed to be moving in the direction of *between* the mirrors. See that picture. If the observer was traveling … how to say it … “along* one of the mirrors(?) … the I don’t think there would be any effect at all.

Am I misreading what you’re saying? (Does the picture make sense?)

Small issue:

In Problems2-Notebook.pdf, the links are broken.
But of course we can still scroll to access the content.

Length is only contracted in the direction of motion. The distance between mirrors is perpendicular to the direction of motion. So I think the mirrors are 1 ls apart in both frames.

I agree with the posted solution if we tally round trips, or double that if we tally 1-way trips.

PS … Also remember that I made the pictures. So if I make a mistake, the pictures could be wrong.

The mirrors are indeed .8 ls apart in the moving frame. I’m not exactly clear on what’s happening when you do the ltrans on x at the end, but take a look at the picture on the third page of the “notebook” that I posted up at the top of the thread. See if that makes sense of things. The mirrors are moving in the observer’s frame, so the light takes…[Read more]

I’m not able to attend today, apologies! I’m doing a birthday party for my oldest. I’ll also be missing next week as I’ll be camping. Apologies!

I got the same answers for everything except 5. For that one, rather than evaluating time I went down the path of counting bounces by distance.

So:
d = distance between mirrors = 1 lightsecond
gamma =…[Read more]

Sorry about that. It wasn’t stated very clearly. What I had in mind was how many “round trips” (from one mirror to the other and back again). So, in other words (if I’m thinking clearly at the moment) then an observer traveling with the mirrors would see 5 “bounces” in 10 seconds. So, yes, the same mirror.

But of course the other interpretation…[Read more]

For problem 5, I interpreted the question
“How many times will the light pulse bounce between the mirrors”
as
“How many times will the light pulse bounce off any mirror”
whereas the solution appears to be answering
“How many times will the light pulse bounce off the same mirror”.

If it’s the former, the proper time between bounces is 1 second…[Read more]

Note that the “index” on the first page of the notebook PDF I just posted about above doesn’t work. Just scroll down or go to the next page in your PDF viewer. Sorry about that.

I’ve also posted some pictures that I might put up while working a couple of the problems. You might want to download this PDF in advance. When I tried sharing my Zoom screen with these they looked a bit hard to read.

I just posted an answer sheet up above. I had meant to spend more time on this, but I decided it was better to get it up there so that people could compare their answers to what I got. I doubt we’ll have time to work all the problems on Sunday. So between this and answers that other people post, when Sunday comes we can concentrate on whatever…[Read more]

Yes, if you have time that would be good.

Would you like us to post solutions here?

Clarification on problem 6

We are looking for a frame where the two events will occur two seconds apart in time.

In other words, we’re not trying to contract the 3 light-second spatial distance. We’re trying to find a frame where the time between the events is two seconds. This is not a simple dilation or contraction problem.

The second problem set is posted above (and I’ve also posted the slides and the video in the thread for yesterday’s meeting).

Video and Slides posted above.

Posted Scott’s slides above.