Pasco OS-8500 INTRODUCTORY OPTICS SYSTEM Manuel d'utilisateur télécharger pdf (Page 40)

Introductory Optics System 012-02744K

Figure 14.2 Depth of Field

Figure 14.3 Chromatic Aberration

Depth of Field

In addition to spherical aberration, aperture size has an important effect on another variable of image

focusing; depth of field. Depth of field is a measure of how much the distance between the lens and

screen can be varied while still retaining a well focused image (see Figure 14.2).

To investigate this phenomenon, begin with the Variable Aperture fully open. Measure the depth of

field. Now vary the size of the aperture, measuring the depth of field for each size.

➀ How does depth of field depend on aperture size? __________________________________

__________________________________________________________________________.

➁ Why is it not possible to have a depth of field that is infinitely long? ___________________

__________________________________________________________________________.

With the aperture size very small (less than 1 mm), remove the lens from the Component Holder.

➂ Is an image of the Crossed Arrow Target still visible on the screen? ____________________

__________________________________________________________________________.

➃ How do variations in the size of the aperture affect the focus of the image? ______________

__________________________________________________________________________.

➄ How does varying the distance between the Variable Aperture and the Viewing Screen affect the magni-

fication of the image? ________________________________________________.

➅ Why does a very small aperture allow formation of an image without using the lens? (Hint: consider

the role played by the lens in focusing the diverging rays from a point object.)

Chromatic Aberration

Replace the lens and remove the Crossed Arrow Target from the Light Source. Using a small aperture

size (2-3 mm), focus the filament of the Light Source onto the screen. Slide the aperture plates slowly to

one side, away from the optical axis of the lens, as shown below. Do not change the size of the aperture.

Notice the color separation in the image of the filament as the aperture gets sufficiently far from the

optical axis of the lens.

➀ Why is chromatic aberration more apparent when the aperture is far from the optical axis of the lens?

__________________________________________________________________.

Crossed Arrow

Target

Viewing Screen

Depth of Field

Lens

Variable

Aperture

Viewing Screen

Lens

Aperture open 2-3 mm

Variable Aperture Displaced

From The Optical Axis

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 74 75

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Pasco OS-8500 INTRODUCTORY OPTICS SYSTEM Manuel d'utilisateur Page 40

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