[Spherical Mirror Reflection]
Dan: Oh great, a mirror.
I want to see how my hair...Whoa, what is up with this mirror, JJ?
JJ: This mirror is not the flat mirror that you're used to.
It is, in fact, two mirrors.
One side is a convex mirror, one that is shaped like this.
The other side is a concave mirror shaped like this, on this side.
Dan: What are we going to do with that?
JJ: In this experiment, we are going to try to experimentally determine
the radius of curvature of this concave mirror.
Dan: If we had a big sphere made out of mirror, and we cut a little part of it off
and made a mirror with it, it'd be the radius of that sphere is the radius of curvature.
JJ: That's exactly right.
If it was a sphere, that concave section, if you're looking from the inside out,
that would be the piece that's in here.
Dan: OK. What do we need to do?
JJ: The instructions first tell us to put our light source here at the 6 cm mark,
and then put our mirror at the 20 cm mark.
The distance between the light source, or this cross-hatched pattern here,
which is going to be our object, and the mirror is 14 cm.
Dan: Object distance starts out at 14.
I can put that in, so it'd be 0.14 meters.
JJ: Right, so our object distance...
Dan: We need the image distance.
How do we do that?
JJ: What we need to do is, there's this little half screen in here,
and the way the half screen works is light from our object passes through the opening,
hits the mirror, is reflected back,
and then it's given a chance to form a real image right there
on the white part of that screen.
Dan: Yeah, I can see something there, but it's a little out of focus.
JJ: Right.
To figure out what our image distance is, we need to figure out the position for this
half screen where the picture of this, the image of this, is in clear focus.
Since I can see it a little bit easier, I'm just going to go ahead and move this.
I can slide it back and forth, and you see right about there is where
this is in focus the best.
Now, the whole thing is not exactly in focus, but this is where most...
Dan: The best.
JJ: Yeah, exactly.
Dan: Yeah, like being at the eye doctor.
JJ: That's right.
Dan: This would be the image distance now from the mirror to where we form the image.
JJ: That's exactly right.
Dan: What do we got there?
JJ: The distance is 7.6 cm.
Dan: OK. I think we need four more data points.
I think we move the mirror out, how about 3 cm?
JJ: Perfect.
I'll slide this from 20 cm to 23.
Dan: That image went out of focus, so we need to move it.
JJ: OK. We move that.
Dan: Our object distance is now 0.17, an additional 3 cm.
JJ: OK. Then the new image distance is 7 cm exactly.
Dan: OK.
Move it another 3.
You might as well just keep going back the same distance.
JJ: OK, 3 more centimeters.
Now the distance between the object...The object distance is 20 cm, right?
Dan: Right.
JJ: We move this.
There is where we get a clear focus image, and that is 6.7.
Dan: OK.
It's going down a little bit each time as we increase the object distance.
JJ: All right.
We'll do three more with the mirror, so now our object distance is 23 cm
and our image distance is 6.4 cm.
Dan: OK. One more.
JJ: One more?
Three cm, so now we've got what?
Dan: 26 total.
JJ: 26 total, yeah, for our object distance, and the image distance is right there, 6.1.
Dan: Now we have all our data in this Capstone file,
and so your job is to look at the relationship in the data and draw some conclusions,
and try and use that for some analysis and synthesis questions.