Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

# Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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Geometrical Optics
Diffraction
Interference
video  - Interference and Diffraction
Multiple Slit Interference
Multiple Slit Interference II
Diffraction using CD
video  - Newton's Rings
Laser Interference
video  - Thin Film Interference
Michelson Interferometer
Color
Polarization
The Eye

### video  - Interference and Diffraction

#### Purpose:

Shine a laser beam through single, double and multiple slits of different widths and spacing on a Cornell multiple slit film.

#### Procedure:

This demo is the same as  video  -  Interference and Diffraction .

Set the stand so that the different patterns can be projected onto the wall or screen. The film holder can be moved in X & Y and secured by two thumbscrews to hold different patterns steady. On the film there are four different columns of slits. The first of these is a series of single slits varying in width. The second is a continuously varying single slit that gradually resolves itself into a varying double slit. The third and fourth sets are of multiple slits of various spacings. The middle pattern in the third row has the most slits, thus giving the sharpest interference pattern. The fifth is a series of double slits of the same width that vary only in their spacing.

#### Hints:

• It is best to use the apparatus at the back of any of the rooms, and shine the diffracted or interfered laser light onto the projector screen. It's best to use projector room in for Rm. 203, but more practical to use a table on the side steps half way up the student seats.
• By request a red or green laser can be used. The green laser is brighter and can be used w/out dimming the room's lights but is very noisy. The old red laser needs ceiling lights off but the contrast for the minima and maxima for closely spaced patterns is better.