Download Make your own Telescope

Make your own Telescope
STUDENT WORKSHEET
OBJECTIVES
1.
To build a refracting telescope
WHAT YOU NEED
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Black cardboard poster sheet
Blu-tac
Ruler
2 x convex lenses with different focal lengths (e.g. 5cm and 30cm focal
length)
scissors
tape
WHAT TO DO
1. Add the lengths of the two lenses. Your cardboard tubes will need to be able to
extend to at least this length.
2. Make a cardboard tube 10cm in length from the black cardboard. Use blu-tac to
secure the largest convex lens in the end of the tube.
3. To calculate the length for the second cardboard tube add the focal lengths of the
two lenses and subtract 5cm. Tape the cardboard closed to form a tube with one end
slightly wider so that it will slide over the first tube. Use blu-tac to secure the smallest
convex lens in the narrow end of the tube.
4. Slide the second, longer tube over the first.
5. Now use the telescope to view distant objects. You need to place the smaller lens
(the longer tube) closest to your eye.
QUESTIONS
1. Calculate the magnification of your telescope.
2. Is the image you see using the telescope, real or virtual?
3. Use a ray diagram of the telescope to show how the image is formed upside down.
RESOURCES used to develop this activity
1. Optical Society of America. 2008. Exploring the Science of Light - Make a telescope.
http://www.opticsforkids.org/futurescientists/intermediate/maketelescope.html.
Accessed 7 September 2009.
© Gaffney, L., and Harper, A. 2009. Queensland University of Technology.