PURPOSE: Observe the Balmer series in hydrogen.

DESCRIPTION: The discharge tube provides an electrical discharge through low-pressure hydrogen, resulting in the characteristic hydrogen spectrum. The Balmer series of lines is visible. The spectrum can be observed using hand-held holographic diffraction gratings in small classrooms. Due to brightness limitations, the spectrum will be shown using a video camera and rear projection TV in the lecture halls, using a holographic grating taped to the lens of the TV camera.

The bright lines seen in the photograph above are (left to right) the source tube, the faint blue line (n=5 to n=2), the cyan line (n=4 to n=2), and the red line (n=3 to n=2). The faint continuum between the cyan and the red lines is part of the sequence of molecular hydrogen transitions.

SUGGESTIONS:

REFERENCES: (PIRA 7B10.10)

EQUIPMENT: Power supply with hydrogen tube, holographic gratings.

SETUP TIME: None.