Optics

Now that we have a basic understanding of light and the color spectrum of visible light, how do we actually see light? One could easily write several books about the intricacies of how the eye functions. But let’s take a quick look at the basics. Remember, light travels in waves. These light waves enter our eyes through the cornea and lens. The cornea and lens work together to focus the light onto the retina. The retina is full of cells (rods and cones) that change the received light waves into nerve impulses that are then collected by the optic nerve and sent to the brain to be interpreted. It is important to understand that a person’s eyes simply help deliver information to his brain. The brain has to then sort out the information and interpret it. We generally take this capability for granted, but try to do the following experiment to understand how our brains are involved in the seeing process.

Are You Seeing This?

Take a look at the picture below. What do you see?

Most people see a white circle. But look carefully; there really isn’t a circle anywhere—just straight lines. Your eyes automatically filled in the missing information in order to see the circle. This is actually an amazing part of how our brain can interpret the light that is sent to it. Without this capability, we would be unable to identify objects that are only partially visible.

Also, there is a still image of a very unique optical illusion. To experience this motion machine, log onto www.ExplorationEducation.com; click on “activities” and then click on “optics.”

Practical Applications

The practical applications of thermal imaging are endless. Following is just a brief list.

  • Search and rescue
  • Detecting fires in a home or forest
  • Diagnosing disease
  • Identifying heat loss in a house so it can be insulated better
  • Law enforcement—search for and identify suspects in buildings
  • Weather forecasting
  • Military—locating targets, gathering intelligence, surveillance
  • Personal Application

Many people wish they could see God and the spiritual world. Some people feel that just because you cannot see something, then it must not be there. But that would be like saying, “I cannot see ultraviolet light, so it must not exist.” Indeed, often what we don’t see affects us much more than what we do. Second Corinthians 4:18 says it this way: “While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.” Remember, it is the eternal things that are the most important.

Enjoy your science!

Published on May 20, 2009


John Grunder and his wife Susan began homeschooling in 1993 and recently graduated their oldest of four. For fifteen years John taught science, math, and technology at Christian and public schools. In 2002 he started Exploration Education™ and has authored both elementary and intermediate homeschool science curricula. For more information and additional science activities, visit their website: www.ExplorationEducation.com.

Copyright 2008. Originally appeared in The ld Schoolhouse Magazine, Winter 2008/09.
Used with permission. Visit them at
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