zz Distinguish between the types of light telescopes. Illustrate how light refracts through convex and concave lenses.
Astronomers study the night sky to better understand space. Light telescopes have allowed us to look at space for hundreds of years.
The Light Telescope
A light telescope uses visible light to produce magnified images of distant objects. Light telescopes use lenses and curved mirrors to focus on distant objects.
There are three types of light telescopes: z Fig. 26.2.1 A light telescope
Learn more about how the eye works in Physical World 19.2
z Fig. 26.2.2 Convex and concave lenses
1. Refractor telescopes use lenses to refract light. This focuses an image of a distant object on the retina in the eye of the person looking through the telescope. z z
Convex lenses converge light to a point. z z Concave lenses diverge light away from a point.
Convex lens
Convex lens
Concave lens
Concave lens
Back of mirror
2. Reflector telescopes use plane and curved mirrors placed at different angles to reflect light. The type of curved mirror used is a concave mirror. This reflects light to a point in front of the mirror. Nearly all large modern astronomical telescopes are reflectors. This is because mirrors are lighter and easier to clean than lenses. They are also easier to make.
z 444 444 Fig. 26.2.3
A concave mirror reflecting light
Concave mirror
3. Combination telescopes use a system of mirrors and lenses to reflect and refract light.
