Sunlight heats the Earth and oceans to create weather. Sunlight powers photosynthesis in plants to grow trees and vegetables.
Sunlight lets us see. Sunlight looks white, but the rainbow tells us light consists of colors red, orange, yellow, green, blue and violet blended together. Sunlight takes eight minutes to travel the 90 million miles to Earth even at 186,000 miles per sec, the speed of light. A light year, the distance traveled by light in one year, has even entered the vocabulary of children when the movie, "Toy Story" featured the hero Buzz Lightyear.
Today's physics lesson was prompted by the article, "Eye and Camera" by George Wald appearing in a commemorative edition of "Scientific American" detailing his research about the biology and optics of the eye and camera. His work in 1950 won the Nobel Prize for medicine 17 years later. Today his discoveries are taught to elementary and high school students in New York state.
The author’s grandson, Jonah, plays with his toy, “Buzz Lightyear,” the hero of the “Toy Story” movie.
Photo by Rachel Greszler
As a matter of fact, to prepare for this article, I found the most information in the junior section at the James Prendergast Library. Yes, the thin, colorfully illustrated junior books describe complex physical and biological concepts in an understandable way.
Since I have a lot to learn about the natural world, I search for subjects on the computer card catalog in the adult section of the library. Usually, half of the pertinent books are in the junior stacks. There, I smile as I pass the librarian who smiles back. I would like to tell her I am really very young but aged prematurely even though I look and feel 68 years old. I confessed to the young lady at the checkout counter I learned more from the junior books than from the adult books. She admitted similar experiences.
Light is a bundle of energy behaving like a particle and a radio wave. When light strikes an object and is absorbed, heat is produced. The concept of light traveling as a wave is difficult to understand. A reasonable explanation is to compare waves in water that result when a pebble is dropped into the smooth surface of a small pond or pool. Ripples or waves spread away from the spot where the pebble was dropped. These tiny water waves have energy which will be felt when they hit the shore to move a small stone or twig. Likewise light has energy which produces heat.
One form of solar power occurs when sunlight heats numerous silicon solar panels and moves electrons thereby generating electricity for household lighting or powering the International Space Station. Light is a form of electromagnetic radiation with longer wave length than high energy X-ray waves, which penetrate the body, and shorter wave length though harmless low energy radio waves, which transmit cellphone and television signals.
When light enters a denser medium like water or glass, the light is slowed and bent, which is called "refraction." Refraction of light by the eye bends light from a large panorama to focus the entire scene to a spot on the retina the size of a pin head. When the cornea and lens bend the light too much, nearsightedness exists while farsightedness results from insufficient bending of light. Ophthalmologists and opticians make glasses and contact lens to refract or bend the light to correct the abnormal light bending.
Light entering the eye creates an inverted or upside down image on the retina. The brain flips this image so we appreciate an upright world. Each eye transmits a separate image to the brain which is combined so one object appears instead of two, fortunately in three dimensions. Specialized, light-sensitive, cone-shaped cells in the retina send impulses to the brain designating color and shape. Rod-shaped cells, sensitive to subdued night light transmit only shades of gray. That is why all cats look gray at night.
Today just happens to be Bring Your Child to the Library Day. Visit your community library; you will be thrilled by what you can learn. Call 484-7135 for information.