InterviewSolution
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InterviewSolution
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How is the working of a telescope different from that of a microscope ? The focal lengths of the objective and eyepiece of a microscope are 1.25cm and 5 cm respectively. Find the position of the object relative to the objective in order to obtain anangular magnificatio of 30 in normal adjustment. |
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Answer» Solution :Working differences `:` 1. OBJECTIVE of a telescope forms the image of a vey far off object at, or within, the FOCUS of its eyepiece. The microscope does the same for a small object kept just beyond the focus of its objective. 2. The final image formed by a telescope is magnified relative to its size as SEEN by the unaided eye while the final image formed by a microscope is magnified relative to its ABSOLUTE size. 3. The objective of a telescope has large focal length & large aperture while the corresponding for a microscope have very small values. Given `:``f_(0) = 1.25cm` `f_(e ) = 5 cm` Angular magnification m = 30 Now, `m = m_(e )xx m_(0)` In normal adjustment , angular magnifucation of eyepiece `m_(e ) = ( d // f_(e )) = ( 25)/( 5) = 5 ` Hence,`m_(0) = 6` But `m_(0) = ( v_(0))/( u_(0))rArr =-6 = ( v_(0))/( u_(0))` `v_(0) = - 6 u_(0)` Applying lens equation to the objective lens `:` `(1)/( f_(0)) = ( 1)/( v_(0)) - ( 1)/( u_(0))` `(1)/( 1.25) = ( 1)/( - 6u_(0)) - ( 1)/( u_(0))` `(1)/( 1.25) = ( - 1- 6)/( 6u_(0))` `6 u_(0) = 1.25 xx ( - 7)` `u_(0) = ( - 12.5 xx 7 )/( 6) cm` `= 1.46 cm` |
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