Pasco OS-8520 PHOTOMETER Manuel d'utilisateur télécharger pdf (Page 4)

Photometer 012-05631A

Experiment 2: Polarization

Polarized

Light

Unpolarized

Light

First Polarizer

No Light

Second Polarizer

Figure 2.1: Unpolarized light incident on two polarizers

oriented perpendicularly to each other.

First Polarizer

Unpolarized

Light

Polarized

Light

Polarized

Light

I = I

cos

Second Polarizer

Figure 2.2: Unpolarized light incident on two polarizers

oriented at an angle φ with respect to each other.

EQUIPMENT NEEDED

– Optics bench (OS-8518) – 2 Point light sources (OS-8517)

– Photometer with filter set (OS-8520) – 2 Polarizers (OS-8520)

Purpose

The purpose of this experiment is to show that the intensity of the light transmitted through two

polarizers depends on the square of the cosine of the angle between the axes of the two

polarizers.

Theory

A polarizer only allows light which is vibrating in a particular plane to pass through it. This

plane forms the “axis” of polarization. Unpolarized light vibrates in all planes. Thus if unpolar-

ized light is incident upon an “ideal” polarizer, only half will be transmitted through the

polarizer. (Since in reality no polarizer is “ideal”, less than half the light will be transmitted.)

The transmitted light is polarized in one plane. If this polarized light is incident upon a second

polarizer, the axis of which is oriented such that it is perpendicular to the plane of polarization

of the incident light, no light will be transmitted through the second polarizer (Figure 2.1).

However, if the second polarizer is oriented at an angle so that it is not perpendicular to the first

polarizer, there will be some component of the electric field of the polarized light that lies in the

same direction as the axis of the second polarizer, and thus some light will be transmitted

through the second polarizer (Figure 2.2).

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Pasco OS-8520 PHOTOMETER Manuel d'utilisateur Page 4