Reflecting Telescope

(a) List some advantanges of a reflecting telescope, especially for high resolution astronomy. (b) A reflecting type telescope has a large mirror for its objective with radius of curvature equal to 80 cm . What is the magnifying power of telescope if eye piece used has a focal length of 1.6 cm ?

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Refracting Telescope

The objective of relfecting telescope is

Sumati wanted to see the stars of the night sky. She knows that she needs a telescope to see those distant stars. She finds out that the telescopes, which are made of lenses, are called refracting telescopes and the ones which are made of mirrors are called reflecting telescopes. So she decided to make a refracting telescope. She bought two lenses, L_(1) and L_(2) . out of which L_(1) was bigger and L_(2) was smaller. The larger lens gathers and bends the light, while the smaller lens magnifies the image. Big, thick lenses are more powerful. So to see far away, she needed a big powerful lens. Unfortunately, she realized that a big lens is very heavy. Heavy lenses are hard to make and difficult to hold in the right place. Also since the light is passing through the lens, the surface of the lens has to be extremely smooth. Any flaws in the lens will change the image. It would be like looking through a dirty window. Sumati bought not-so-thick lenses for the telescope and polished them. What advantages, if any, would she have with her choice of lenses?

Sumati wanted to see the stars of the night sky. She knows that she needs a telescope to see those distant stars. She finds out that the telescopes, which are made of lenses, are called refracting telescopes and the ones which are made of mirrors are called reflecting telescopes. So she decided to make a refracting telescope. She bought two lenses, L_(1) and L_(2) . out of which L_(1) was bigger and L_(2) was smaller. The larger lens gathers and bends the light, while the smaller lens magnifies the image. Big, thick lenses are more powerful. So to see far away, she needed a big powerful lens.Unfortunately, she realized that a big lens is very heavy. Heavy lenses are hard to make and difficult to hold in the right place. Also since the light is passing through the lens, the surface of the lens has to be extremely smooth. Any flaws in the lens will change the image. It would belike looking through a dirty window. Based on the diagram shown, what kind of lenses would Sumati need to makethe telescope?

A refracting telescope consists of

Describe a reflecting type telescope. What are its advantage over the refracting telescope ?

Assertion : A reflecting type telescope is preferred over refracting type in astronomy. Reason : Reflecting type telescope is free from chromatic aberration and parabolic surfaces are used to avoid spherical aberration.