The desired overall magnification of a compound microscope is $140 \times .$ The objective alone produces a lateral magnification of $12 \times .$ Determine the required focal length of the eyepiece.
So in this problem, the overall desire magnification off a compound microscope is 140. And I'm using negative Scient because that indicates the images upside down. And the literal magnification of the objective lens is 12. And I'm using natives and for that as well, because the image is inverted. So we know that the overall magnification M is actually the product. So we know overall magnification M is the product of the lateral magnification of the objective and angular, more magnification of the eyepiece. So from here, we can actually write down m e equals em over, and one which is going to be negative 1 40 over negative tools. And this would give me I'm just gonna ride down positive value of that. So it is 1 40/12 All right, now, we also know that M is 25 centimeter over f e. So that means 25 centimeter over Effie is 1 40/12 All right, so from here, you can see that actually, f is going to be 25 times troll over 1 40 and this is going to give me two point once, and David er