PASCO OS-8459 Beginning Optics System - Manual (Page 37)

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M o d e l N o . O S - 8 4 5 9 E x p e r i m e n t 1 2 : M i c r o s c o p e
37
Analysis
To calculate the magnification complete the following steps and record the answers in
Table 12.1:
1. Measure d
o1
, the distance from the object (paper pat-
tern on screen) to the objective lens.
2. Determine d
i2
, the distance from the eyepiece lens to
the image. Since the image is in the plane of the
object, this is equal to the distance between the eye-
piece lens and the object (screen). Remember that the
image distance for a virtual image is negative.
3. Calculate d
i1
using d
o1
and the focal length of the
objective lens in the Thin Lens Formula (Equation
12.1).
4. Calculate d
o2
by subtracting d
i1
from the distance
between the lenses.
5. Calculate the magnification using Equation 12.2.
6. Calculate the percent difference between the calcu-
lated magnification and the observed value.
Questions
1. Is the image inverted or upright?
2. Is the image that you see through the microscope real or virtual?
Further Study
Image Formed by the Objective Lens
Where is the image formed by the objective lens? Is it real or virtual? Us a desk lamp
to brightly illuminate the paper grid (or replace the screen with the light source’s
crossed-arrow object). Hold a sheet of paper vertically where you think the image is.
Do you see the image? Is it inverted or upright? Remove the sheet of paper and hold a
pencil in the same place. Look through eyepiece lens; you will see two images, one of
the pencil and one of the grid pattern. Are both images inverted? Use parallax to
determine the location of the pencil image.
Increasing Magnification
While looking through your microscope, move the objective lens a few centimeters
closer to the object. Which way do you have to move the eyepiece lens to keep the
image in focus. How close can you move the objective lens and still see a clear
image? (Make a pencil mark on the paper grid so you have something very small to
focus on.) What is the theoretical limit to how close you can move the objective lens?
Table 12.1: Results
Position of Objective Lens
Position of Eyepiece Lens
Position of Screen
Observed magnification
d
o1
d
i2
d
i1
d
o2
Calculated Magnification
Percent Difference