ZingPath: Space Technology

There are many different types of telescopes. We are most familiar with those that examine the visible spectrum of radiation. There are telescopes designed to look at virtually every area of the electromagnetic spectrum. Each different wavelength of light carries its own picture of our universe that scientists can gradually add to our ever-changing model. There are also terrestrial and space-based telescopes. Telescopes can also be linked to form vast arrays that act as one large telescope. None of these advances in technology would have been possible without the simple glass lens.

The glass lens has been in existence since at least 424 BCE when a burning glass was mentioned in a play by Aristophanes. It took almost 2,000 years before scientists began publishing their observations using lenses to make microscopes. At about this time, Galileo began to use his lenses to observe the stars. Johannes Kepler (1571-1630) added to Galileo's work by defining the laws of planetary motion and laying some of the groundwork in physics that Isaac Newton would eventually use for his invention of Calculus. It was not until Isaac Newton published his book "Optiks" in 1706 that scientists were able to really understand how lenses worked and how we could exploit the properties of light and glass to make new discoveries. Now scientists can design lenses for a specific purpose and know exactly how they will work before going to all the trouble of grinding and polishing a lens.

Converging and diverging lenses are both able to change the direction of propagation of light rays in specific ways. By understanding the properties of these lenses, scientists can manipulate the way an object is viewed to suit their needs. A converging lens is also known as a convex lens. It is thicker at the center than at the edges. This causes light that enters the lens on one side to converge at a point on the other side. The point of convergence is called the focal point.

A diverging lens also known as a concave lens is thinner at the center than at the edges. Light that enters on one side diverges on the other. The true focal point of this type of lens is actually on the same side of the lens as the light entering the lens. This type of lens is used in some telescopes. Converging lenses cause an image to appear to originate from a focal point behind the lens.