00:01
All right, so we have a mirror with an image from infinity being produced in front of it.
00:06
So i'm going to do my best to kind of draw all of these lines in this diagram sort of proportionally.
00:14
So let's say this is like sort of the central axis of the mirror.
00:17
The mirror is located here.
00:19
And we're told that an image from an object basically at infinity.
00:24
So our object distance, b0, is infinite.
00:28
It produces an image at 25 centimeters.
00:33
So we want to know from this information, what's the focal length of this mirror? so we use our familiar mirror equation, which is one over the image distance plus one of the object distance equals one over the focal length.
00:46
We can see when the object distance is infinite, basically, this term disappears.
00:52
And so we just have the equality between the image distance and the focal length.
00:56
So for this particular mirror, we have a 25 centimeter focal length.
01:02
Now we want to know if we place an object at a distance 30 centimeters from the mirror, where is it going to end up, what's the height of it going to be, and things like that.
01:15
So i'm going to do my best to draw all of this kind of proportionally to figure out what the ray diagram would look like, which i don't think you really need this in the problem, but you might as well draw it.
01:27
Um we're going to have the lights being reflect oops the light is going to be reflected through the focal point of the mirror and the image will be formed where the another line or another ray is drawn through the focal length um on the near side of the mirror so kind of like this oh i'm not the best with this pin um sorry should be able to get it this time all right so i've got these lines kind of drawn.
02:22
So the mirror needs to be a little bit bigger to fully capture the image i'm going for.
02:27
So maybe we'll say it looks kind of like this.
02:29
But our image distance is going to be produced following this line...