Pasco OS-9257A PRECISION INTERFEROMETER Manuel d'utilisateur télécharger pdf (Page 25)

012-07137A Precision Interferometer

Experiment 2: The Index of Refraction of Air

Reference to  Procedure

1. The chamber will be properly aligned when the reflec-

tions off the front and back end-plates are aligned with

each other and with the main interference pattern. (This

alignment may actually cause a secondary interference

pattern, but it will be very faint and will not affect your

measurements.)

2. It seems easiest to apply the vacuum first, then count

the fringes as the vacuum was released.

The average slope, starting at a guage reading of 60,

was 3.462x10

-6

0.9995

0.9996

0.9997

0.9998

0.9999

1.0001

1.0002

1.0003

1.0004

1.0005

0 102030405060708090

Pressure (cm hg)

Answers to  Questions

1. Extrapolating from our slope and the known index of

refraction of vacuum,

atm

= 1.000263.

2. Measure the index of refraction at various pressures,

and see if it increases linearly. (It does.)

3. Answers will vary; but they should include some way

of heating the air on one arm of the interferometer

without heating the air on the other arm or the inter-

ferometer itself.

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Pasco OS-9257A PRECISION INTERFEROMETER Manuel d'utilisateur Page 25