# Microscope calculation

1. Oct 22, 2009

### lha08

1. The problem statement, all variables and given/known data
If the field diameter on 40X is 1600 µm, and a specimen takes up one quarter of the field, how big is the specimen in real life?

2. Relevant equations
Magnification of image= Image size/ Real size of object

3. The attempt at a solution
I'm not sure but in the formula, would be put the magnification of the image as 40 and image size as 1600 µm and solve? or would we simply find one quarter of 1600 µm and that would be the actual size of the specimen..? I'm a little confused so could help me clear things up about the differences between the two?

2. Oct 22, 2009

### mgb_phys

Ignore the quarter for now.

If the magnification is 40x and the image is 1600um then what is the real size of the object (hint the microscope makes things look BIGGER!)

3. Oct 22, 2009

### lha08

Umm...I'm not really sure but all i can think of is that the magnification is 40 which is equal to 1600um divided by the real size of object and do i solve for the unknown?

4. Oct 22, 2009

### mgb_phys

Ignore the algebra an just think whats happening.

If the magnification was 2x then the object would appear twice as big as it really is.
If it appears 1600um then it must really be 1600/2 = 800um

5. Oct 22, 2009

### lha08

So in this case, the magnification is 40x so the object is 40 times bigger than the actual size, so 1600/40= 40 um?

6. Oct 22, 2009

### BAnders1

Good, now if the specimen takes up a quarter of this space, how big is it?

Last edited: Oct 22, 2009
7. Oct 22, 2009

### lha08

ahh oki so a quarter of 40 um is equal to 10 nm (that's the answer?)

8. Oct 22, 2009

### BAnders1

If you have any doubt as to what the answer is, CONVINCE YOURSELF. What if you were a ridiculously tall Titan of 100ft whose naked eye could only focus on something as close as 4 inches away? Let's say some funny fellow Titan created a device (we'll call it a microscope) which could focus on things up to the unheard of size of ONE CENTIMETER (wow!!!). Now let's say you were a titan studying the complexities of a human pupil. If your Titan microscope could focus up 10X, and the pupil covered 1/4 of this size, how big would you say a human pupil was, after viewing it through the microscope?

What I'm trying to say is that we aren't allowed to tell you if your answer is correct or not, thus you must think of some extreme situation to test the answer yourself.