PASCO Specialty & Mfg. OS-8459 Manuel d'utilisateur télécharger pdf (Page 33)

Model No. OS-8459 Experiment 11: Telescope

1. Measure d

, the distance from the object (paper pat-

tern on screen) to the objective lens.

2. Determine d

, 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

using d

and the focal length of the

objective lens in the Thin Lens Formula (Equation

11.1).

4. Calculate d

by subtracting d

from the distance

between the lenses.

5. Calculate the magnification using Equation 11.2.

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 telescope 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? Use 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.

Object at Infinity

Remove the screen and look through the lenses at a distant object. Adjust the distance

between the lenses to focus the telescope. Estimate the observed magnification.

Now calculated the magnification by taking the ratio of the focal lengths of the lenses.

Compare the calculated magnification to the observed magnification.

How is the distance between the lenses related to their focal lengths?

Table 11.1: Results

Position of Objective Lens

Position of Eyepiece Lens

Position of Screen

Observed magnification

Calculated Magnification

Percent Difference

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 50 51

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PASCO Specialty & Mfg. OS-8459 Manuel d'utilisateur Page 33

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