Question

question 4
which of the following best describes the focal length of a telescope?
it is the distance from the lens or mirror to the object being viewed.
it is the diameter of the telescopes primary lens or mirror.
it is the radius of the telescopes primary lens or mirror.
it is the distance from the lens or mirror to the image formed of a distant light source.

Explanation:

The focal length of a telescope is defined as the distance from the lens or mirror to the image formed of a distant light - source. The first option is about object - distance, not focal length. The second and third options refer to the size (diameter and radius) of the primary lens or mirror, not the focal length.

Answer:

It is the distance from the lens or mirror to the image formed of a distant light source.