For thousands of years people have used many creative tools to understand what they saw in the sky. Stone Hedge in England was a tool used by ancient people to keep track of the movements of the stars. The Indians of the North American Continent made giant circles in the dirt which pointed to different stars. And an ancient device allowed sailors to measure the distance of the North Star from the horizon. But no inventions have helped scientists more than the inventions of first the lens, and then later the parabolic mirror.
Since we cannot actually visit distant stars and planets, we have to rely on the light they send to us. Almost everything we know about these distant objects we have learned by studying their light.
Telescopes use lenses or mirrors to bend light. The light is bent so that it focuses into a point. Have you ever used a magnifying glass to bend light. If you hold it just right you can focus the light into a point and burn a hole in wood. Once bent into a point, light can then be magnified using another lens. This is done two different ways.
The traditional type of telescope called a refracting telescope uses two lenses, one to bend the light, and then another to magnify it. A reflecting telescope uses a mirror to bend the light, and then a lens to magnify it.
Assignment # 3.
In your own words explain how a refracting telescope bends light and then magnifies it.
Explain how a reflecting telescope bends light and then magnifies it.
Check your answer
A refracting telescope uses two lenses one to bend the light, and then another to magnify it.
A reflecting telescope uses a mirror to bend the light, and then a lens to magnify it.