Question

identify the pros and cons of using mirrors versus lenses in each of the following applications:

• a large, ground-based, astronomical telescope
• a small “spy” scope
• a terrestrial telescope designed only to read license plates

Answer 1

Solution:

If lenses are used, it is a refractor telescope. If mirrors are used, it is called a reflector telescope

In an astronomical telescope, both the objective and eye piece are convex lenses. Focal length is large for the objective.but eye piece is of short focal length.

When using mirrors, chromatic aberration is eliminated.

cons: But the image is not focussed properly at a single point and there will be a dragging effect.

Pros : Using a large focal length objective helps in collecting more light coming from the star. Small focal length eye piece serves as a magnifying lens and forms a larger image.

Cons: Chromatic aberration is the defect that arises from a telescope using the lenses.

It forms an inverted image.

In a terrestrial telescope, the final image formed finally is upright.

Lenses are used to bend the light coming from the sources.

Terrestrial telescope is longer in size than an astronomical telescope and is also more expensive.

Spy glass is a small telescope that can be taken from place to place ( portable).

They are more comfortable to use and give an upright image.