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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 1.25 cm and 5 cm respectively. Find the position of the object relative to the objective in order to obtain an angular magnificationof 30 in normal adjustment. |
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Answer» Solution :A TELESCOPE produces images of far objects nearer to our eye. Therefore, objects, which are not resolved at far DISTANCE, can be resolved by looking at them through a telescope. On the other hand, a microscope magnifies objects (which are near to us) and produces their larger image. In nutshell, thus, a telescope resolves whereas a microscope magnifies. As per question `f_(0)= 1.25 cm,f_e = 5 cm` and `m = 30`The compound microscope is being used in normal adjustment i.e., final image is being formed at `infty` `therefore` Magnification or eyepiece `|m_(e)| =D/f_(e) =(25 cm)/(5 cm) =5` As `|m| =|m_(0)| xx |m_(e)| = 30/5=6` `rArr |v_(0)/u_(0)| =6`. But as the image formed by objective lens is real and inverted one, hence as per sign convention `u_0`is negative and magnification is ALSO negative i.e., , `m=-6` or `v_(0)=-6u_(0)` Thus from lens formula `1/V-(0)-1/u_(0) = 1/f_(0)`, we have `1/(-6u_(0)) -1/(-u_(0)) =1/1.25 rArr 5/(6u) = 1/(1.25) rArr u=1.5 cm` |
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