Physics Demo Number: 039

Approximate Run Time: 8 min

Mercury (Hg) Atomic Spectrum System

Demo Description

One uses a Pasco Mercury Light Source ,with a dedicated [broad slit , diffraction grating, lens ]- system attached, and breaks its intense light up into a few very broad lines from the mercury spectrum .

These lines are intense enough to be focused on a screen in the lecture hall and seen easily.

This technique allows the instructor to be sure that all reasonably attentive students have seen the lines.

One can use fluorescing material (on a two surface hand-held screen) to observe some near ultraviolet lines from the source as visible lines.

Scientific Principles

• Atomic Spectrum of Mercury

• Fluorescence

Equipment

• Pasco Mercury Lamp

• Broad-slit diffraction-grating-lens system

• Two surface Screen

Equipment Location

• All the cited equipment resides in Kit [039] in [A-2-2]

Instructions

The picture shows the Pasco Mercury Light Source with dedicated broad-slit diffraction-grating-lens system attached. One should plug the light's power cord into an extension cord beforehand, so that the unit may be turned on and left burning continuously during the whole class period. It takes 3 to 5 minutes for the light to reach maximum intensity.

One may display the spectral lines directly on the wall or a screen. There are two near-ultraviolet lines that can be seen on surfaces with appropriate fluorescent dyes but not easily or at all otherwise. There is a special half-white half-yellow screen in the Kit that works well for showing the invisible ultraviolet lines.

Writeup created by David A. Burba

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