a telescope to observe distant stars. He got the idea, from a spectacle maker who one day observed that the distant weather cock appeared magnified through his lens system fitted in his shop. Galileo observed the satellites of Jupiter and the rings of Saturn through his telescope. Kepler invented Telescope in which was fundamentally similar to the astronomical telescope.
Types of Telescope According to optical property, it is classified into two groups: i) refracting telescope ii) reflecting telescope In refracting telescope lenses are used. Galilean telescope, Keplerian telescope, Achromatic refractors, are some refracting telescopes. In reflecting telescope parabolic mirrors are used Gregorian, Newtonian, Cassegrain telescope are some Reflecting telescopes According to the things which are observed, Astronomical Telescope and Terrestrial Telescopes are the two major types of telescope. Astronomical Telescope An astronomical telescope is used to view heavenly bodies like stars, planets galaxies and satellites.
Terrestrial Telescopes The image in an astronomical telescope is inverted. So, it is not suitable for viewing objects on the surface of the Earth. Therefore, a terrestrial telescope is used. It provides an erect image.
The major difference between astronomical and terrestrial telescope is erecting the final image with respect to the object. Advantages of Telescopes Elaborate view of the Galaxies, Planets, stars and other heavenly bodies is possible. Camera can be attached for taking photograph for the celestial objects. Telescope can be viewed even with the low intensity of light.
Disadvantages Frequent maintenances needed. It is not easily portable one. Figure . Image formation in compound microscope Points to Remember Light is a form of energy which travels along a straight line The deviation in the path of light ray is called refraction.
The ratio of speed of light in vacuum to the speed of light in a medium is defined as refractive index ‘µ’ of that medium. Lens formula f = ν – u Magnification (m) = h ' h = ν u Power of lens. P = f The ability of the eye lens to focus nearby as well as the