Pasco OS-8500 INTRODUCTORY OPTICS SYSTEM Manuel d'utilisateur télécharger pdf (Page 65)

012-02744K Introductory Optics System

Exp 10: Polarization

Suggestions on – Procedure

➀

The target is not as bright when you look through

the polarizer. This is because half of the light is

blocked: the half that is polarized in the wrong di-

rection.

➁ The light source is not polarized. There is no effect

when the polarizer is rotated, so the light source

must be randomly polarized.

➂ With polarizer A set at 0°, there is a maximum

when polarizer B is at 0° or 180°. The minimum

occurs when B is at 90° or 270°. Note that the

minimum is not zero: some light will still be trans-

mitted due to the fact that the polarizers used do

not completely polarize the violet or the deep red

light.

Brewster’s Angle

➀ The reflected light is plane polarized at 90° from

the vertical.

➁ At other angles of reflection, the light is partially

polarized; with the degree of polarization depend-

ing on the angle of incidence.

➤➤

➤Notes: It may be interesting to call attention

to the effect of polarizers on digital watches.

LCD displays work by having a polarizer just

above a liquid crystal cell. When an electric field

is applied to the liquid crystal, it polarizes light at

90° to the permanent polarizer, and blocks the

light. This is what makes the black numbers seen

on the display. If you look at a digital watch

through a polarizer, it will be completely black at

certain angles.

Another effect that can be tied into the investiga-

tion of Brewster’s angle is reflection off water.

Such a reflection will be partially polarized, as in

section 2 of the Brewster’s angle part of the lab.

Polarized sunglasses make use of this; they are

polarized in the opposite direction to cut glare.

Exp 11: Image Formation from Cylindrical Mirrors

Focal Point

➀ 58 mm

➁ 59 mm

➂ The reflected rays will be parallel.

Image Location

➀ 65 mm from the mirror

➁ As the mirror moves closer to the filament, the im-

age distance lengthens.

➂ Yes, it is a virtual image located on the opposite

side of the mirror from the filament.

➃ Only if you use the cylindrical lens as well.

Magnification and Inversion

➤➤

➤Note: There are two ways of moving the

filament. One is to just slide the entire lamp

some distance to the side and measure that

distance. Another is to rotate the filament holder

so that the filament is even with one edge of the

lamp window, then rotate it to the other side. In

the second method, h

is just the width of the

window.

➀ The amount of magnification decreases with dis-

tance from the object.

➁ The image is inverted, and the inversion does not

depend on distance.

Cylindrical Aberration

➀ The rays do not all focus to the same point.

➁ Make a parabolic mirror instead of a cylindrical

one.

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Pasco OS-8500 INTRODUCTORY OPTICS SYSTEM Manuel d'utilisateur Page 65

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