Optics B/C

[cngu23]

The rules this year are very explicit about having some sort of covering over the mirrors. And it's been discussed numerous times in this forum. How could you not know about that?

It was my naivety, I practiced with only one type of cover, and it was really easy to take off. I've learned my lesson...

18. If atmospheric refraction did not occur, how would the apparent time of sunrise and sunset be changed?
a. Both would be later.
b. Both would be earlier.
c. Sunrise would be later, and sunset would be earlier.
d. Sunrise would be earlier, and sunset would be later.

Can someone help explain this?

[foreverphysics]

Both would be earlier.
When light passes through the atmosphere, it gets bent and has to travel for a greater distance, therefore needing more time to travel before hitting Earth.

[Infinity Flat]

The rules this year are very explicit about having some sort of covering over the mirrors. And it's been discussed numerous times in this forum. How could you not know about that?

It was my naivety, I practiced with only one type of cover, and it was really easy to take off. I've learned my lesson...

18. If atmospheric refraction did not occur, how would the apparent time of sunrise and sunset be changed?
a. Both would be later.
b. Both would be earlier.
c. Sunrise would be later, and sunset would be earlier.
d. Sunrise would be earlier, and sunset would be later.

Can someone help explain this?

The atmosphere scatters and refracts light, so more than half of the Earth is illuminated at any given time. If there was no atmospheric dispersion of light, than exactly one half of the Earth would be illuminated. That is, the days would be shorter than with the atmosphere. Thus, sunrise would come later, and sunset would be earlier. (C)

[foreverphysics]

Oh, oops. I was thinking in terms of sunset. Guess I forgot about the sunrise part.

[TAZmaniandevil]

Hey! Does anybody know any last second study tips? Our regional contest is this weekend... still confused about how to trace convex/concave mirrors!!!

[cngu23]

Hey! Does anybody know any last second study tips? Our regional contest is this weekend... still confused about how to trace convex/concave mirrors!!!

Get your templates for the laser shoot ready. That's 40/100 points right there. On my regionals, I messed up with the side of the laser shoot templates cause I didn't prepare enough for that portion. For tracing mirror diagrams, just go to the scioly wiki and copy the diagrams there for reference. Most of the other things can be found in a Physics textbook.

[bigbrown2520]

What's the best resource for questions that have a state feel to them? What do they tend to focus on in the geometric part v. the physical optics part?

[winneratlife]

Get your templates for the laser shoot ready. That's 40/100 points right there.

Can someone explain to me what's so hard about the laser shoot? Not trying to be pretentious; I'm legitimately curious.

I walked in there with one of those 45-45-90 triangle template thingies, set up 4 mirrors on 45s, walked out with a gold. Obviously I didn't use all 5 mirrors, but I'm starting to wonder if I got lucky, because I know of teams that go to huge lengths to prepare for the laser shoot and miss totally...

[tuftedtitmouse12]

The problem with more mirrors is that there is a greater chance of the angle not reflecting right. Also, you have to be sure to put the middle of the mirror at the intersection of the lines. Also, not knowing where the barrier is located means that either you have to make several different templates for different situations or you have to learn how to draw and set down the mirrors quickly within the 4 minutes. Anyways, congrats on the gold!

[cngu23]

The problem with more mirrors is that there is a greater chance of the angle not reflecting right. Also, you have to be sure to put the middle of the mirror at the intersection of the lines. Also, not knowing where the barrier is located means that either you have to make several different templates for different situations or you have to learn how to draw and set down the mirrors quickly within the 4 minutes. Anyways, congrats on the gold!

You can walk in with like 4 small squares of paper with 45 degree angles on them. (May be my backup, just in case something fails.) You don't necessarily have to align the center of the mirror along with the line. No matter where the laser hits, if you put the mirror at 45 degrees, the laser will always bounce off at the same angle. You just need to make sure that the reflected ray hits the next mirror.