question_answer 11)

A compound microscope consists of an objective lens of focal length 200 cm and an eye-piece of focal length 6025 cm separated by a distance of15 cm. How far from the objective should anobject be placed in order to obtain the final imageat (a) the least distance of distinct vision (25cm), (b)infinity ? What is the magnifying powerof the microscope in each case ? 

Answer:

Here, Distance between object lens and eye piece= 15 cm (a) For the formation of image at the least distance of distinct vision, from the relation, we have or Negative sign tells that the object for the objectlens lies to the left of the lens. Distance of the image from the objectlens = 15 - 5 = 10 cm Usingweget or or Magnifying power, (b) When the final image is formed at infinity,then the object for the eye lens must beplaced at its principal focus. Therefore, and Now using or