Solving Optic Lens Problem: Find Object Distance for Magnification of 75

[mithil03]

Homework Statement

Suppose we have a microscope made out of two lenses, both with a focal length of
25mm, placed 36.5mm apart. Find how far in front of the first lens should the object be
placed to assure that the image is magnified at least by a factor of 75?

One more:
Suppose that we have a positive lens with radii 60 and 100 and thickness of 3 (any units,
as long as you are consistent), with an index of 1.5. If an object with a height of 10 is
placed at a distance of 100 from the lens, find at what distance from the back surface is
the image formed. DO NOT treat this as a thin lens.

Homework Equations

The Attempt at a Solution

The first one, couldn't understand how to calculate for magnification factor of 75

Help please...

 

[berkeman]

Homework Statement

Suppose we have a microscope made out of two lenses, both with a focal length of
25mm, placed 36.5mm apart. Find how far in front of the first lens should the object be
placed to assure that the image is magnified at least by a factor of 75?

One more:
Suppose that we have a positive lens with radii 60 and 100 and thickness of 3 (any units,
as long as you are consistent), with an index of 1.5. If an object with a height of 10 is
placed at a distance of 100 from the lens, find at what distance from the back surface is
the image formed. DO NOT treat this as a thin lens.

Homework Equations

The Attempt at a Solution

The first one, couldn't understand how to calculate for magnification factor of 75

Help please...

Why didn't you list the lens equation as a Relevant Equation? That's why we have that line in the Homework Help Template.

List the Lens Equation, and show your work to solve the first question.

Then, what is different about the 2nd question? What equations apply when you can't use the thin lens approximation?

We do not do your work for you here at the PF. We can offer hints and ask questions, but we do not open your textbook for you and do your reading...