Math 309 Final project

The Light Microscope

Written by: Erh-Tsu, Wei

Student number: 75078014
Short introduction of light microscope.

In general, the convex lens' magnification rate wont be very big, because of the aberration limit; But if we combine two convex lens, then it may result in a bigger magnification. The microscope is designed by two convex lens. The lens which use to approach the object is called the objective lens, the focal distance for it is very short, the lens aperture is smaller. The lens which approach the eye is called the eye lens, the focal distance for it is very long, the lens aperture is bigger.

When put object F in the distance farther than the objective lens focal point f1, the objective lens create its upside down enlargement real image, and causes this picture to fall inside the eye lens focal point f2; Therefore the viewer may see upside down enlargement virtual image which its creates by the eye lens.

Because the object has been enlarged after using objective lens and eye lens, therefore we may see the object in a greatly enlarged virtual image the by using the microscope.
How does the microscope get the work done?

Generally speaking, magnifying glass enlargement percentage because of aberration limit, about 20 times; If we want a greater magnification, we must need to use the microscope. The microscope made by two lens compose (namely objective lens and eye lens), and its magnification M is objective lens' magnification M1 times eye lens' magnification M2.

If P1 and Q1 separately expressed the distance of the object and the first institute become picture objective to the lens, then objective lens magnification M1 may under the type expression:

M1 = - Q1/ P1

The light travels like the picture below:

<Click the image to get the *.ps file>

Now we place the second lens after the focal plane of the first lens, and it will work like the picture below:
<Click the image to get the *.ps file>
Now the first imagery is located in the eye lens focal distance, the second imagery is located the person eye the near-point, therefore the eye lens function just like an ordinary magnifying glass.

Conclusion:

The eye lens and the objective lens work in the same way, so after we put those two lens systems together, we will get the microscope magnification:

M = M1* M2

For the common light microscope, its maximum magnification is about 1,500 times which is large enough for human eyes to see some tiny objects through it. Thats how the microscope get the enlarge work to be done.