Mitch Is an Optometrist and His Niece Has Asked Him

Multiple Choice

Mitch is an optometrist and his niece has asked him to come to school to talk about his profession at a job fair. Mitch is trying to impress his niece's classmates by telling them cool things about ocular health and the way the visual system works.
-Mitch starts explaining how we are able to see and begins by explaining the way light works.He explains that humans are able to see variation in the saturation of colours due to differences in the ______ of light.

A) speed
B) amplitude
C) wavelength
D) purity