What is Telescope is also the related topic to the geometrical optics.
Telescope is an optical instrument which is used to observe
distant objects using lenses or mirrors. A telescope that uses
two converging lenses is called refracting telescope
(Fig.12.34). In refracting telescope an objective lens forms a
real image of the distant object, while an eyepiece forms a
virtual image that is viewed by the eye.
The ray diagram of refracting telescope is shown in Fig.12.35.
When parallel rays from a point on a distant object pass
through objective lens, a real image I1 is formed at the focus
F0 of the objective lens. This image acts as an object for the
eyepiece. A large virtual image I2 of I1 is formed by the
eyepiece at a large distance from the objective lens. This
virtual image makes an angle q at the eyepiece.
Magnification of a refracting telescope can be determined
through the ray diagram of Fig. 12.35 and is given by M=fo/fe
1. Astronomical telescope
2. Galilean telescope or Terrestrial telescope
Astronomical Telescope is an instrument that is employed to check the enlarged image of distant heavenly bodies like stars, planets, satellites and galaxies etc.
The final image formed by an astronomical telescope is always virtual, inverted and magnified.
An astronomical telescope works on the principle that once associate degree object to be enlarged is placed at an over sized distance from the target lens of telescope, a virtual, inverted and enlarged image of the article is created at the smallest amount distance of distinct vision from the attention control about to the attention piece.
An astronomical telescope consists of 2 convex lenses : Associate in Nursing objective lens O and an eye fixed piece E. the distance FO of the target lens of scope is giant as compared to the distance metal of the attentionpiece. and also the aperture of objective lens O is giant as compared thereto of eye piece, in order that it will receive additional lightweight from the distant object and type a bright image of the distant object. each the target lens and also the eye piece ar fitted at the free ends of 2 slippery tubes, at an acceptable distance from one another.
Differences between Astronomical Telescope and Galilean Telescope
|S No.||Astronomical Telescope||Galilean Telescope|
|1.||An astronomical telescopeis associate degree instrument that is employed to check the increased image of distant heavenly bodies like stars, planets, satellites and galaxies etc.||A Galilean Telescope or a terrestrial telescope is an optical instrument which is used to see the magnified image of distant objects on earth.|
|2.||It consists of two convex lenses.||It consists of a convex objective lens and concave eye piece.|
|3.||The final image formed by astronomical telescope is always inverted.||The final image formed by Galilean telescope is erect.|
|4.||Its magnifying power is high.||Its magnifying power is low.|
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