Question

what is terrestial telescope explain its working rule and its ray diagram

Answer 1

1. Telescopes use lenses to gather more light than the human eye could collect on its own. They focus the light and make distant objects appear brighter, clearer and magnified. This type of telescope is called a refracting telescope.

A (refracting) telescope consists of two convex lenses: The larger lens is called the objective lens, and the smaller lens used for viewing is called the eyepiece lens. Here the image of the distant object formed by the objective acts as the object for the eyepiece.

The size of an image produced by a lens is proportional to the focal length of the lens. The longer the focal length, the larger the image. The brightness of an image from a telescope depends partly on how much light is collected by the telescope. The light-gathering power of a telescope is directly proportional to the area of the objective lens. The larger the lens, the more light the telescope can gather. Brightness of images also depends on how big an area the image light is spread over. The smaller the area, the brighter the image. The magnifying power of a telescope depends on the focal length of both lenses.