The Dow Jones industrial average fell 22.22 points, to 10,488.07, and the Standard & Poor's 500 index decreased 2.98 points, to 1,131.13.

The Standard & Poor's 500-stock index decreased 23.03 points, or 2 percent, to 1,150.53.

The broader Standard & Poor's 500-stock index decreased 9.78 points, or 0.9 percent, to 1,136.76.

The refractive index decreases with increasing wavelength.

In graded-index fiber, the index of refraction in the core decreases continuously between the axis and the cladding.

The Standard & Poor's 500-stock index decreased 3.28 points, to 1,036.30, and advanced 1.7 percent this week.

The Standard & Poor's 500-stock index decreased 18.76 points, to 1,389.07.

Almost all optical materials that are transparent for visible light have a normal, or positive, dispersion: the refractive index decreases with increasing wavelength.

The Standard & Poor's 500-stock index decreased 5.30 points, to 1,101.39, and declined 1 percent for the week.

However the refractive index of the ionosphere decreases with increasing frequency, so there is an upper limit to the frequency which can be used.