How do humans perceive color? a. the optic nerve acts like a prism and separates white light into colors. b. photoreceptors on the retina detect different wavelengths of light. c. the pupil of the eye varies in size to absorb different wavelengths of color. d. the lens of the eye interprets the colors of the visible spectrum.

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.