In an Internal Focusing Telescope

By Aina Parasher|Updated : July 26th, 2022

In an internal focusing telescope

  1. The objective is at a fixed distance from the diaphragm
  2. The focusing is done by the sliding of a divergent lens
  3. The focusing divergent lens is situated at about the middle of the tube
  4. All the above

Answer: D. All the above

In an internal focusing telescope the objective is at a fixed distance from the diaphragm, the focusing is done by the sliding of a diverging lens and the focusing divergent lens is situated at about the middle of the tube.

Solution

In the internal type of focusing telescope, objective and eyepiece lenses are mounted at a fixed distance from the diaphragm and focusing is done by the movement of diverging lens (concave lens).

Some important points:

Length of internal focusing telescope is lesser than the external focusing telescope.

Line of sight is less likely to be affected because eyepiece and objective lenses are fixed.

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