On Vision and Colors are, however, nonessential properties that differ according to the type of light-refracting substance that is used. The top of the upper image is violet. Below the violet is blue. The bottom of the lower image is orange. Above the orange is yellow. In this way, along with the white disk and the black background, four prismatic colors appear: violet, blue, yellow, and orange. This is in disagreement with Newton's claim that there are seven prismatic colors. As the upper image overlaps black, it is seen as violet. Where it overlaps white, it is seen as blue. As the lower image
Spectrum Sound in our environment that we refer to as "noise" includes many different frequencies. When a sound signal contains a mixture of all audible frequencies, distributed equally over the audio spectrum, it is called white noise. The spectrum analyzer is an instrument which can be used to convert the sound wave of the musical note into a visual display of the constituent frequencies. This visual display is referred to as an acoustic spectrogram. Software based audio spectrum analyzers are available at low cost, providing easy access not only to industry professionals, but also to academics, students and the hobbyist. The