An optical instrument uses eye-lens of power 16 D and objective lens of power 50D and has a tube length of 16.25 cm. Name the optical instrument and calculate its magnifying power if forms the final image at infinity.

Explanation

`P_(e) = 16 D rArrf_(e) = 1/P_(e)=1/16 m = 100/16 cm =25/4cm`
`P_(0)=50 D rArr f_(0) = 1/ P_(d)=1/50 m=100/50 cm=2 cm`
`f_(e) = 25/4 cm and f_(0) = 2 cm`
length of tube = l= 16.25 cm
Optical instrument is compound microscope.
`M= L/(f_(0)) xx D/(f_(e))" " =16.25/2 xx cancel (25)/cancel (25)_(4)=16.25 xx 2`
M=32.5