Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

To make a Telescope

Introduction

Telescopes are used to view distant objects with a larger angular magnification. An important aspect of telescope is resolution for which one needs a convex lens of large aperture as the objective. Here we make a very simple telescope to give the feel and excitement.

Apparatus

A concave lens of focal length 5 cm, a convex lens of focal length 20 cm and same radius, a transparency sheet, double sticky tape, cellophane tape.

Procedure

  1. Put the transparency sheet on a horizontal surface, peel off a length of the double sticky tape (15 cm) and stick it on the transparency sheet. The length should be slightly more than the perimeter of the lenses.
  2. Now stick another piece of tape of same length, parallel to the first piece at a separation of exactly 15 cm (20cm - 5cm). Remove the upper non sticky cover to expose the sticky surface.
  3. Carefully put one of the lenses on a tape in vertical orientation and the other lens on the other tape parallel to the first one.
  4. Now roll the sheet very carefully, keeping the two lenses parallel to each other. After one complete roll, use cellophane tape to securely fix up the roll.
  5. The telescope is ready. Keeping the concave lens towards eye, look at distant objects and enjoy. Write your experience with this telescope.

Note

Figure to be made