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(a) Draw a labelled ray diagram of an astronomical telescope to show the image formation of a distant object. Write the main consideration required in selecting the objective and eyepiece lenses in order to have large magnifying power an dhigh resolution of the telescope. (b) A compound microscope has an objective of focal length 1.25cm and eyepiece of focal lenth 5 cm. A small object is kept at 2.5 cm fromthe objective. If the final image formed is at infinity, find the distance between the objective and the eyepiece. |
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Answer» Solution :(a) For diagram Alternatively ,  For large magnifying power `f_(0) `should be large and `f_(E)` should be small. For higehr resolution DIAMETER of the objective should be large. (b) `(1)/( v_(0))- ( 1)/( U _(0)) = ( 1)/( f_(0))` `(1)/( v_(0)) = ( 1)/( f_(0)) +( 1)/( u_(0)) = ( 1)/( 1.25) - ( 1)/( 2.5) = ( 1)/( 2.5)` `v_(0) = 2.5 CM` ` L = | f_(0)| +| f_(e)|``( :. v_(0) = f_(0) )` `= ( 2.5 + 5.0 ) cm = 7.5 cm` |
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