9.2 Experimental part

1. Switch on a LASER and receive the interference pattern.

2. Draw this picture in your own notebook and measure the distance between max in different places. For example:

y = S / ( N – 1 ). (9.3)

3. Fill the table 9.1

Figure 9.1

Table 9.1

№	Si , mm	yi , mm	, mm	L , mm	d , mm	Λ, nm
1					0,22
2
3

4. Measure the distance L between the plate with slits and screen.

5. Calculate the length of a laser light wave by this formula:

, (9.4)

where d - is the distance between two parallel slits, d = 0.22 mm.

6. Calculate the errors for these measurements.

Conrtol questions

1. What is the phenomenon of interference?

2. What are the coherent waves?

3. Why are there max and min on the screen?

4. What are conditions of max and min of interference?

5. What are the factors that influence the distance between interference bands?

References

1. Ландcберг Г. С. Оптика. – М.: Наука, 1976.- с. 62 – 94.

2. Сивухин Д. В. Общий курс физики. – т. 4. – М.: Наука, 1980.- с 188- - 256.

3. Савельев И. В. Курс общей физики.– т. 2. – М.: Наука, 1982.- с. 347 – 374.

Authors: Lushchin S.P., the reader, candidate of physical and mathematical sciences.

Reviewer: Loskutov S.V., professor; doctor of physical and mathematical sciences

10 LABORATORY WORK № 63

INVESTIGATION PHENOMENA OF POLARIZATION

OF LIGHT

The aim: to study the phenomena of polarization of light, checking Malus’ law.

Instrumentation and appliances: laser, analyzer, mirror, photocell, microammeter.

10.1 The short theory

Light is a transverse wave. The direction of the vibrating electric and magnetic vectors are at right angles to the direction of propagation ( Fig.10.1 ).

Figure 10.1

Light is emitted by a great number of atoms. The plane of oscillations of vector is not the same in space. The orientations of this vector as well as vectorare arbitrary ( Fig. 10.2a ).

This is so called a natural or unpolarized light. If there is an interaction of light and substance the effect of polarization takes place.

Figure 10.2

A plane polarized wave is shown in Fig.10.2b. The plane of oscillations of vector is regulated. There are three ways of producing a polarized light: reflection of light; refraction of light; transmission of light through anisotropic substance ( calcite crystal CaCO₃ ).

According to the law of Malus, the intensity of light transmitting through the analyzer can be calculated by the next formula

, (10.1)

where I is a transmitted intensity ; I_m is the maximum value of the transient intensity, it is equal to the intensity of light, falling on the analyzer; θ is the angle between the plane of polarizer and the plane of analyzer.