00:01
All right, so in this problem we have an object that is 5 centimeters in height, and it is placed some distance away from a concave mirror.
00:12
And we know that the focal length of the mirror is 3 centimeters, and we know that the image is found 4 .5 centimeters behind the mirror.
00:21
Now, at this point, i drew the focal length inside of the object, but that doesn't necessarily mean that the object is on this side of the focal length.
00:38
It might be inside the focal length.
00:40
We'll have to figure that out as we go, because we're looking for that distance from the mirror to the object.
00:51
So we're going to use the mirror equation to figure this out, where 1 over f is 1 over the focal length, and 1 over d o is 1 over the object distance, and 1 over d i is 1 over the image distance.
01:11
And so we're going to have to solve this for that d o.
01:15
So first we'll subtract this term from both sides, and then we'll take the inverse of it...