A refracting astronomical telescope has an objective of focal length fo=120cm and an eyepiece of focal length fe1=6cm. It is used in normal adjustment.
(a) Calculate the magnifying power of the telescope in this arrangement.
(b) The eyepiece is replaced by another lens of focal length fe2=4cm while the objective is kept the same. Determine the new magnifying power.
(c) Compute the percentage change in magnification between the two eyepieces.
(d) Discuss briefly why, in practical instruments, reducing fe beyond a certain limit does not necessarily improve the quality of observation.