111 Spectra

Instructional note: Spectrometers made from boxes and CDs were used. Both the continuous solar spectrum and a discrete fluorescent light spectrum were observed by the students.

Copy paper box spectrometer using CD eye hole: look in here lightslit copy paper box CD at roughly 45 ° angle Cut away side view of box

Traditional colors of the visible spectrum in English: Red Orange Yellow Green Blue Indigo Violet. Indigo was apparently inserted by Newton to have seven colors in the "rainbow" as opposed to six.

Red Orange Yellow Green Blue Indigo Violet

Below red: infrared heat radiation. Microwaves. Radio waves. Alternating current.

Beyond violet: ultraviolet. Can cause sunburn, skin cancer. Even higher frequencies include x-rays and cosmic rays (cosmic radiation).

Continuous versus discrete spectra

If gas discharge tubes are available, a demonstration of continuous versus discrete spectra can be done.

Continuous spectra

discrete spectra

A rainbow is a continuous spectrum produced by the sun. All of the colors "blur" into the next color, there are no distinctive separations in the colors. The sun produces light as a result of being very hot. Things that produce light by getting hot produce continuous spectra.

Discrete spectra

discrete spectra

A gas discharge tube contains one specific gas. Gases produce discrete spectra. The colors do not blur into each other but are separated by gaps where no color appears. Gases with a small atomic number such as hydrogen and helium clearly show separated spectral lines. The lines are related to the nature of the atomic structure of an atom. Atomic structure is a part of a later chapter in this text.