This book covers: Acoustics, Optics of Color, and Geometrical OpticsBefore the Sixth Grade all children have acquired a knowledge of musical intervals, of the keyboard of the piano, and of the different major and minor keys and of their respective notations. Up to the Sixth Grade the musical intervals, as well as the various keys, stand for experiences of specific musical qualities. Then in the Sixth Grade the students are led to realize that these intervals, as well as the keys, also have other sides to them, connections with measurements and numbers. Anyone, even with a relatively poor musical development, but knowing that an octave is made by the tones of a string at half of its length will be able to produce an octave as accurately as it could be done by the keenest musical ear. The scientific facts added to art open up new possibilities.