Why do animals' eyes reflect light? Why metals are opaque. Why do clouds usually form high in the air instead of near Earth's surface? Why do we see swirls of color and dark spot right before the bubbles pop? Why can white light be separated into different colors?
7 to 12% of men have some form of color-vision deficiency (color blindness), and less than 1% of women do. Low-vision conditions increase with age, and half of people over the age of 50 have some degree of low-vision condition. Worldwide, the fastest-growing population is 60 years of...