University of Bristol
Institute of Physics logo
Why not try our other site: BEEP Biology & Ethics

Lenses and telescopes

Newton's telescope

Model of Isaac Newton's first reflecting telescope - Click to enlarge.

Light travels more slowly in materials like glass than it does in air.

That can make the light change direction as it passes between materials. The effect is called refraction.

Symmetrical objects like lenses can refract light in regular ways, to make images.

Your eyes make images by using refraction at the surface where they meet the air.

Activity: Take some convex lenses. (They are the ones that are fatter in the middle.)

Hold one facing a window. Hold a screen made of card or paper on the other side of the lens. If you move the screen around, trying different distances between the lens and the screen, you should be able to make an image of the window and the view outside.

Two convex lenses, a fatter one and a thinner one, can make a telescope. The fatter one needs to be the one nearer your eye.

Use the lenses to see if you can make a simple telescope.

Next: Models of the Solar System

What's your opinion?

Average rating

Not yet rated

Read comments

speech bubble  No comments yet. Why not be the first person to add one?